Genuine question: is it more that the USA has a completely different idea of how race/ethnicity works than the UK? That's the only explanation I can think of as to why both sides seem to be at completely different wavelengths...

... regarding food, I always understood it as essentially being two things. E.g. a Mexican restaurant in USA is Mexican food...adapted for American pallets, and an Indian restaurant in the UK *is* Indian (frequently Bangladeshi) food adapted for British pallets, and so on.

Saying that the cuisine is Italian or Chinese does not preclude the people who make it being American...