I think that the greatest common factor between the different nations that brought corrupt politicians to power was the development of small yet powerful groups of people that were able to speak to the wills of the general public in their own countries. Additionally, the governments in these countries had to be weak enough to not stop these movements or hated enough to drive the vast majority of the general public to the opposite side. Germany is an example of the first (Hitler and the Nazis suspend a weak, powerless democratic government) and the USSR is an example of the second (Tsar Nicholas II's poor leadership drove the majority of the people to communism.)
There are similarities between 1933 and 2010. In both cases, the people, disliking their current government, have switched to supporting another group, promising a change. However, because the democratic government in the United States in 2010 is so strong, and not enough people have passionate enough of a hatred for the government, there is no "extreme" government taking power. Such parties are being created (Tea Party), but they aren't in much power.
Were Germans responsible for Hitler? Yes, but they didn't have much choice. If any country at that time, including the United States, was in as desparate of a situation as Germany, they would have turned to a Fascist leader too. Even now, with our government and economy in a MUCH better position than Nazi Germany, there are still radical groups developing.
