Why is Asian/African American a thing only in America?

I get that Asian and African American terms are used but I don't understand why it's only in America? (At least to my knowlage) I've never heard anyone say "I'm Asian French" or im "African British" and I'm not American and it's not said in my country to identify someone.

It's it a thing and I have just never heard it? Or does it just not exist outside of America?