I feel as though nowadays AC/DC ARE an American band.
AC/DC were extremely Australian, a bunch of bogan lads that loved a drink and a fight and their rock was simple, hard, loud and infectious. I loved them to bits, their early albums with Bon Scott are absolute classics. Rock anthems.
Back in Black, their first album with Brian Johnson singing (following Bon Scotts death) is nothing short of amazing considering the history. Most expected the end of AC/DC as it was hard to imagine them without the larger than life Bon Scott up front. So it was make or break for AC/DC, and Back in Black certainly made it both commercially and most importantly critically, and laid the tracks for a new path.
Since then, they certainly did further 'evolve' their music and appeal to satisfy the far larger market outside of Australia i.e. USA and Europe. Nowadays I don't really consider them much an Australian band. Not that I don't like them or respect them, just that they aren't really catering to their audience here like they did once. I can't blame them, they just went where the money is.....