I buy French Brie at US grocery stores many times a year. Did you mean to say it's one of the types that isn't illegal?
So no, what you buy as brie, if it went through official US import channels, is not real Brie. Now how much is the real difference in taste is another topic, but we take protecting traditional methods of making these things very seriously here in Europe. Very anti-race-to-the-bottom approach.