"His name is Rodric, after his grandfather."
Is this use of 'after' British usage? If so,
what is the American equivalent?
An American would say it the same way, imo.
May I offer some friendly advice? Do not worry so much about "American equivalents" to BrE. I`m an American, and I can tell you that there certainly ARE differences between the two. However, I`ve never been the least bit baffled by BrE, and I can almost say with 100% certainty BrE speakers have NO trouble with AmE. We`re all native speakers after all. This applies as well to English-speaking Canadians, Aussies, & New Zealanders as well. If you`re trying to sound "British", I`d say don`t waste your time. You`ll never lose your native language accent well enough to fool a native English speaker anyway.
Thank you very much for the kind advice. Yes, I wish I could make much effort to be able to speak better English at this age of 71. My interest at this time is in the STUDY of the differences between BrE and AmE.