Hi guys, yes I'm in the car business market, also I have a garage. So my point of view is on a lot of experience on all type of cars.
Americans : 99% salvage cars as @Fredericsaid. For me it's good Cost x Benefit cars, because I dont see accidents as a big issue if it's been fixed properly since accidents happens to GCC cars as well. Sure that you will not have warranty nor service contract on this cars, but in the other hand you are paying much less. Maybe some insurance companies might not accept, but many will... about the heat, I ask you, what temperature does your car work on ? Should be 90 degrees, so do you think that a 50 degrees outside temperature will do any harm ? This "belief " came because most of the cars had a front accident, and many times pipes or radiator were not fixed how it should, that's why some heat problems, what could also happen to GCC cars. AC I never had problems because its American or not.... for me it's a good COST x BENEFIT. Watch out for luxury flooded cars with too many electronics, it can be an issue, but all depends on the conditions of the car..
Japanese: I dont trust in the km, they are always very low, what doesn't make sense. But usually all in good shape.
Europeans : really need to check, I've seen cars that are not available in uae and also accident (salvage) cars.