Here in France, portion sizes tend to be small-ish but the practice of eating multiple courses is very strong. Many people prefer to have starter, main + dessert (even in places like company canteens or when eating at home) but in smaller portions of each. In any kind of social situation this will often be preceded by the apero, where the snacky bits to eat are just as important as the drinks. It can be quite a lot of food overall, but spread over a fairly long time and in small amounts per course.
Whereas in the UK for example, I think more often people tend to just have one or two bigger courses, especially when cooking for themselves at home. And there is no common ritual of having an "apéro" with things to eat as well.
Definitely when we went to America we were amazed by some of the portion sizes! Very, very generous.
All that said, I'd think that 150g of meat per person is generally what I am for, but since we are meat lovers if it ends up more like 250g sometimes, or even more, we generally have no problem finishing it!