50 lbs/ft2 is pretty much the upper limit in the continental US. Most of the Midwest is around 20lb. Maine and Alaska go significantly higher. Pretty much the entire South is 10lb or less.
I've lived various places in the US. With the exception of one older house, the roof trusses were a joke: so-called 2x4's (really much thinner than that), widely spaced, held together with a few nails and little or no cross-bracing. They might theoretically hold up to the weights listed, but I sure wouldn't stand under them during a test.
Where I am now, in Europe, the roof trusses are roughly 6"x10" laminated timber. That will hold a snow load.
