The lack of granularity in America is honestly extremely annoying to me, different states or cities generally have wildly different "white" culture, traditions, commonality, and attitudes. It is often more hidden or subtle and less overt or surface level like it is in Europe.

Equally annoying is when people attempt to define 'African-American' as though it was one homogeneous entity of experience. The experiences and struggles of a young black man in NYC is vastly different from the struggles of a young black man in rural Alabama.

This is the problem with categorization of people in general. All this "you're white", "you're black", "you're male", "you're female" is belittling because it's so surface level and ignores the depth of human experience. There's so much diversity within each of these broad categories.

In America, "white" is used instead of "European" because it's less ambiguous, since it distinguishes Americans of European ancestry from European citizens.

That being said, "white" is also ambiguous in other ways. It's generally not meant to be strictly speaking about skin color, since people with fair skin from certain parts of the middle east, for example, would not necessarily be considered to be white in this context.