Birmingham indeed but particularly The Black Country.

It is an "Americanism" in that it is more commonly used by North American speakers. It is the archaic form of got which has been preserved in American English and not so much in British English. Yes, I don't like its use. To my ear it sounds like an unnecessary affectation when spoken by an obviously British speaker. We are still allowed to dislike things I believe.

What interests me most though is the reason for its apparent rapid rise in use over here. We heard it in American films and TV programmes for decades without it taking off here. Like most American words we knew and heard gotten - like sidewalk, trash, elevator, automobile, hood, gas, windshield, and trunk - but on the whole we didn't normally use it or any of these words. Why has it happened? As you suggest it may be because its use has increased recently in the US too. I've read that suggested somewhere else recently also. The development of language is interesting.

In the North they say "mam", have you seen a card with mam on it?

One effect of that state of flux being that the word "gotten" by and large fell out of favour some time toward the start of the last four hundred years or so. I say by and large because it does seem to have survived as a dialectical form, but I wouldn't say that it was in general use (and still isn't).

Nonetheless, it was sufficiently widespread to prompt the cautionary tale (from either Fowler's Modern English Usage or Brewer's Phrase and Fable, I think):

A man who had promised to take his wife to a very popular show that was typically sold out months in advance managed by some miracle to secure two tickets. Excitited, he sent his wife a telegram* that read "Have gotten tickets". Imagine his surprise when he met his wife at the theatre to find that she had brought with her four other couples...

*Which should tell you that this is by no means a new story

Is it though? Or are you simply guessing? Either way you've made up your own definition.