At least on the US Census people are self-identifying their race which probably is more accurate than any definition you might subscribe to.
When Jessica Alba says she isn't Hispanic, and Cameron Diaz says she is they are talking about their ethnicity not their race.
BTW of the 36 OECD countries the USA has the 5th worse murder rate (5 oer 100,000) - the four countries that have a higher murder rate are
Brazil 22.7 per 100,000
Mexico 19 per 100,000
Russia 11.2 per 100,000
Estonia 5.2 per 100,000
The next highest is Chile with 3.7 per 100,000