Are you saying that we can't say that if the German people had a law similar to the 2nd amendment, then the Holocaust wouldn't have happened? Or are you saying that American's can't use the Second World War, and the Holocaust as validation of their fears that the government might become too powerful?
The was no law like the 2nd amendmend ever in any constitution. I was thinking why that was the case and well, the US was a colony and Europe wasn't. Here you had established "states" ,kingdoms and little principalities, free cities etc and in Prussia at least a strong military. Prussians were very proud or their military and to be in the military or to wear a uniform in general. Most regions in central Europe are densly populated and there was no need to be able to form a militia or to defend yourself (2nd amendment). It is completely different from the history of the US where people were trying to become independant and had to fight with their mother colonoy for it. Revolution in Germany was the opposite - people wanted to unite all the little countries and states to have one german nation-state. The first time Deutsches Reich existed was in 1871. (see graphic below - by 1789 the US was already a republic with 13 states while most of what is germany today was looking like a crazy patchwork blanket)
Whereas in other parts of Europe, such as France or even Poland, coherent nation-states emerged from the early modern trend of political concentration and centralisation, no such state emerged within the Holy Roman Empire. While two relatively large states developed within the Holy Roman Empire, both—the Habsburg Monarchy and the Kingdom of Prussia—were really multinational empires that included substantial non-German territories and lands outside the borders of the Holy Roman Empire.
Apart from these two states, the Holy Roman Empire consisted of hundreds of small, German-speaking principalities, most of which derived from successive dynastic splits, sometimes reflected in compound names such as Saxe-Coburg. During the early modern period, these small states modernised their military, judicial, and economic administrations. These hardly existed at the imperial level, and the emperor was little more than a feudalistic confederal figurehead, without political or military clout. After the Reformation, the Empire's small states were divided along religious lines. Those headed by Roman Catholic dynasties faced those ruled by Protestant dynasties in the Thirty Years' War and other conflicts.
After French Emperor Napoleon Bonaparte forced the Holy Roman Emperor, Francis II, to dissolve the Empire in 1806, Kleinstaaterei was altered but not eliminated. Through the elimination of territories ruled by prince-bishops (secularisation) and through the consolidation of neighbouring principalities, enclaves, and exclaves, Napoleon reduced several hundred states into a relative concentration of a little over two dozen states in the Confederation of the Rhine. This confederation did not survive Napoleon's military defeat at the hands of the allies. These allies included Prussia and the Austrian Empire—the successor state to the Habsburg Monarchy. These two were the only major German powers, and neither had been part of the Confederacy of the Rhine. The victorious allies, including Prussia and Austria, decided at the Congress of Vienna (1814–15) on widespread dynastic restorations, although some of Napoleon's consolidations were allowed to stand, and Austria and Prussia helped themselves to some formerly independent territories. The resulting territorial division resulted in a consolidated version—around 40 states—of the pre-Napoleonic Kleinstaaterei.
The rise of nationalism across Europe brought movements striving for 'nation-states', each governing an entire (ethno-cultural) people. German nationalists began to insist on a unified Germany. This mood led to the pejorative use of the word Kleinstaaterei during this era. The call for a unified nation-state was one of the central demands of the Revolutions of 1848, but the ruling dynasties of the smaller German states and of multinational Austria and Prussia managed to resist nationalist efforts at unification.
Only after Prussian Chancellor Otto von Bismarck gradually built a unified German state under the Prussian royal house of Hohenzollern did Kleinstaaterei largely end in 1871 with the founding of the German Empire. (The only surviving small states —Luxembourg and Liechtenstein—were at the periphery of the German-speaking world.) The founding of the German Empire created a largely German nation-state. (While the German Empire excluded the partly German but multinational Habsburg domains of Austria–Hungary, it included a substantial Polish minority in parts of eastern Prussia and other minorities along its northern and western borders.) The unification of the German Empire put Germany on the map as a major European power, albeit too late to become a major colonial power.
As you can see, the historic developments in Europe are very different from the US. It is implausible to assume something like "Had they been armed" because they weren't. The gun laws that were passed after WW1 were not meant to disarm the civilian population but to disarm the militias (Freikorps) that sprung into existence after 1918. Those were mostely nationalsocialist militias, precursors of the SS and SA. You can't really blame the Weimarer Republik administration(s) for not wanting those to be armed. They had weapons that were leftover from WW1, and the militias consisted mostely of soldiers that were angry that Germany had been forced to sign the treaty of Versailles, taking the whole blame for WW1.
To come back to your first question, yes and no, but mostly to the negative. Yes, if the people had been armed maybe things would have been different. This is pure speculation though. The historic development shows that it just was never something that was overly important. The revolution of 1848 was about bringing all the different countries together to form one german nation and to have civil liberties and rights - it was never about the right to bear arms. Nobody can really say for sure how history and society would have had developed HAD everybody been armed and it is too simple to assume that weapons alone would have been enough to stop the Holocaust. The history of Antisemitism is also fairly complex, and I just read yesterday in the paper that it wasn't until after WW2 that ivy league universities in the US accepted Jews on a regular basis. You had your own share of antisemitsm in US history - according to the author of that article at least, Robert B. Goldmann, a free journalist from NY.
To your second question, americans had been wary of their government and too much power for it even before WW2, right? It is part of your history, having to fight off an opressive british colonial force automatically lead to the conclusion that your own form of government should never be in the same position to be that powerful. So, I would say that you can use it as an example, but that even if you don't you'd still be wary of too powerful governments. I doubt that similar developments that lead up to WW2 and the rise of fascism could happen in similar fashion in the US, but you also know that other things that opressed and killed people did happen during US history, so your government was quite capable of cruelty itself. Is it too low of a blow to call what happened to the Native Americans and First Nation tribes as genocide? Running them off their own lands, breaking every treaty, forcing them into reservations, the indian wars, trail of tears etc. I read somewhere that president Jackson was the closest thing the US had to a dictator. Or McCarthyism and the witchhunt for communists in the 50ies, that was sort of opressive and dictatorial of the government, wasn't it? And now the fight against terrorism and the Patriot Act gave more power to the government than you would normally deem good or sensible - so Nazigermany isn't really the only example that can be used to show what can happen in opressive regimes.
What made the Nazis so devious was that they managed to insert their ideology and the power of their party into every aspect of daily life. You couldn't really seperate private life and official ideology and propaganda after a while. Everybody was in the party and everybody was a nazi to some degree. If you were german, it wasn't really a bad thing most of the time, you had a job or took someone else's job that just disappeared, your kids had fun with the Hitler Youth going camping and learning how to be a soldiers while playing games, the economy was thriving finally again after the big global financial crisis in the 20ies and the germans were finally able to feel good about themselves again. And the Nazis weren't obviously opressive right from the start. That is the true danger one should always be wary about, underhanded propaganda that influences you without you noticing. And I would say that some of that exists in certain areas of the US - for example certain evangelical denominations work with similiar methods of propaganda (I watched Jesus Camp a while ago and I found it truly spooky to see that. The film has no commentary and just shows some of what is happening), and I am sure othere groups do as well. It does not happen at federal or state level, it is not something the government does, but it still influences whole communities.