Well Gracchus I think you've just explained everything.
I was thinking last week how the 'Americans are stupid' claim pretty much universally held to be true, including inside the US, was pretty facile. There are stupid people in every country and I think you've just explained it - large right amygdala.
If people are pretty much the same then the difference is due to differences in the way the countries work.
The US has a huge gap between the rich and the poor and therefore there is a lot of jealousy of the rich. Yes Americans keep lowering the taxes from the millionaires and up, even as many of the very wealthy express a desire to pay more taxes because the country is heading for bankruptcy, but the 'no hopers' continue to vote Republican because they refuse to accept the almost certainty that they will never be rich.
Weird. So if there was a revolution, it would be the poor out in the streets demanding nothing for themselves but just that the rich pay less tax, and that they be allowed to keep their guns as that is the only defense against the government, who they believe was democratically elected.