I din't think you could possibly verify that.a lot of CTers claim to be from America, when they are not.
US might have louder CTs but the Nazi were founded on belief in the Illuminati. The Nazis led by Hitler, have done a whole lot worse than any American so far in the belief of the Jewish Conspiracy theory. Belief in UFOs was around a whole hell of a lot longer than the USA itself. If you take a look at CT history as a whole, and not just western CTs you'll see that your assumption is WAY off. Americans tend to like the little CTs moreso than the bigger CTs. They like to make some CTs popular. In order to, "wake you up." Because the little CTs aren't considered CTs yet in the minds of most people. Mostly because most people wouldn't even dare think of half the stuff they make up. Others might think they are asking reasonable questions, even though they are not. Usually those people haven't been following the story closely enough which is why they are led to believe in "alternate theories." Also a lot of CTers claim to be from America, when they are not. Or they are from America, but they shouldn't be living here as they go off and defend North Korea and Iranian dictatorships...
It's not about origins its about perpetuation. If the USA stopped believing in conspiracy theories en mass, most of them would rapidly sink without trace.
Make your next poll "Americans Are More Likely To Believe Conspiracy Theories" Yes or No.