No, not the United States and Britain, but, the United States and Kenya.
Whilst Amy (see The colour of my skin, below) was staying in Kisii, she gathered some of our kids together and sang an alphabet song to them. Some of them knew it and joined in.
But when she came to the letter Z, she pronounced it "Zee" whereas the kids pronounced it as "Zed", as in British English. This surprised her and also spoiled the song as she was expecting to have to rhyme with Zee.
She mentioned this in an open letter to us. I didn't have the heart to tell her that Kenyans speak English, not American.