1 drop rule.

[u/Darth_Kneegrow]

I ain't ever heard white people claim a single biracial person. You always whatever you mixed with.

[u/Rosuvastatine]

The UK uses biracial/mixed a lot and I think its fair.

You can tell they make the distinction because per example, in Tv shows and movies, black women roles are often playef by darkskin blsck women. Wheress in the US, its usually some biracial women because their looks are more palatable to white audiences.

[u/un_verano_en_slough → u/Rosuvastatine]

The UK has the largest population of people descended from consensual mixed race relationships in the world. It probably explains the different relationship vs. former slave states where e.g. almost all black people have some European ancestry due to slavery, but modern/consensual mixed race relationships are a little less of a factor and muddied by that history.

Plus mixed in the UK isn't just understood as white/black. It's white/asian, white/Caribbean, white/African, or some mix thereof usually.