It is "normal" that the US allows food (additives, at least) that is banned in Europe
And while this lists a bunch of things we have issues with, there are also a few others that might eventually get allowed, but take a long time. Like monk fruit and alluose.
Coumarin is found chiefly in perfumes (functional and fine fragrance) and smells sweet and grassy. In this application, it is sold all over the world, including the US.
As a flavor in food, it is banned in the US.