I bet you if the meteor landed in some place like Canada or England there would 500% less conspiracy theories.
True, but at the same time neither have been modern super powers that have been capable of the large scale insanity of the USA or Russia when they put their minds to it. This isn't to say they don't have their moments, but not quite the same way.
To put things into perspective there is a "real conspiricy theory" about the US goverment "Majestic 12" project, which was a program to use high end brainwashing and deprogramming techniques to plant sleeper agents in other nations which could later be activated with a signal and would make a suicide run on a pre-programmed target like a goverment facility, politician, etc... before killing themselves. All of which are fully in the grasp of high end psychological and chemical techniques if your unethical enough. The problem with the program is of course getting people for long enough to do this, creating the cover identities, and of course the simple fact that things change with time, your sleeper agent is pointless if a target relocates, or the guy you program him to kill winds up out of power, to be replaced by another enemy. There are a lot of practical concerns here.
This of course lead to theories about what would happen if the goverment used this on a more domestic level, to influance policies, create criminal acts that removed people it found inconveinent, etc... Most recently you have some theorizing that The White House might be using similar techniques to cause shootings to fuel anti-gun efforts, especially given the tendency towards self-pwnage of the people responsible for these sprees, and general lack of reporting on backstory or motivation outside of a very general sense.
Now it's not LIKELY, but a conspiricy theory like that comes about in the US because we really did screw around with ideas like that, and what's more it could actually happen in theory. With Canada or the UK it's not likely, because there is no indication the goverment was ever involved in anything like that. If they were it was kept quiet enough to not be excposed and thus doesn't fuel the public imagination the same way.
In a more relevent comparison, I pointed out in a previous post here, that during The Cold War, there were apparently programs, at least at a hypothetical level, about basically dropping meteor-like rocks and objects on the planet as an alternative to nukes. The very discussion raises questions when something like this happens in one of the countries that was known to have been hosting it.
If the UK, Canada, or other countries ever become more powerful again in the current era and start operating on the same level, conspiricy theories will also rise in proportion to it. The US and USSR used to be involved in this kind of crap and indeed we occasionally saw things "leaked" with an eye to freaking the other side out, etc... It was all part of the game. Canada for example has never to my knowlege been even remotely accused or suspected of developing super science weapons with an idea towards global military assetiveness... who why would Canadians even suspect something their goverment did might have slipped?