U.S. network TV isn't fond of accents. Execs don't think U.S. viewers can understand them, which, to a certain extent, is true. As long as he's working on TV here, I doubt you'll be hearing anything but the American accent. Sorry!
I'm just glad his dialects are always spot-on. I am an accent snob, and couldn't believe it when I found out he was British after watching most of BSG. His is impeccable (maybe from having an American father?) At any rate, he even flawlessly does different American dialects, which is even more impressive. Makes me love him all the more.
He's talked in interviews how his father being American has made it easier to do the accent. He also visited the U.S. growing up. Not that he doesn't struggle with some words (he still slips up on "been" from time to time ;), but the exposure he's had to the American accent I'm sure made his job less of a struggle. :)
Many of the guest shots he'd be up for in U.S. shows are probably written as American before he's cast, in such a way that it wouldn't make as much sense to change it. Not all are, though. Crossing our fingers he gets a regular gig next pilot season, who knows what might get thrown his way. Thing is, the fact he does such a good American accent opens up tons more work to him, which is a plus. (For him AND us. ;) )
Joss Whedon doesn't seem to mind accents, part of what's to love about him. I know his ability to do the American accent well makes him much more palatable to a larger audience. I know my grandmother can't watch anything with accents. She doesn't understand "those foreigners". (please hear the implied closed-minded derision in that)
I guess I just came of age in the 80's when all the coolest musicians were British and MTV still talked about music so I'm used to it. British accents are a huge bonus. I'm trying to raise my kids on Doctor Who so they end up on the right side of this.
I think you and are are about the same age. ;) And I love a good accent as much as the next person (probably a tiny bit more). Still, I get that there are going to be certain characters where it just makes more sense; just going off the very brief clip here, the House character plays like your outwardly "perfect" upper middle-class WASP (possibly conservative) nuclear family man, so with that context (and what follows), in an American series it seems logical for him to go Yank.
Will totally grant you (per your comment below) that Perception seems like a role, from what little we know now, that might allow for him to use his own accent.
Makes him more marketable. Hugh Laurie is a "household face" and it's because his American accent is so clean [Blackadder feels like a dream], so this is good news for us because it means he gets more work and not just as the "British Bad Guy" [sexy as that may be].
And I agree with the comments about some Americans' aversion to accents. I've tried to introduce some people to LOUK and heard grumbles about the accents [to which I say, "if you can't understand this, it's because you don't want to, those accents are easy"].
But Chase has an accent, right? So sometimes it can work. I have hope for that show he's going to be recurring on (Perception?) because British works on a professor, doesn't it?
The main cast accents are pretty easy in L&OUK but I will say sometimes the witnesses/suspects are tougher to understand. Really sometimes the New Yorker suspects/witnesses on the original L&O are tough to understand too. I think both shows feel it adds to the "grittiness" of the big city. I'm trying to get my friends/family into L&OUK, offering the first season DVDs but no one will take me up on it. :-(
I got my uncle hooked on the first season. He's been bugging my mom and I for months about when Season 2 will be on DVD (he doesn't get BBCA).
Chase does have an Australian accent, but it's fairly subtle compared to many I've heard. The character was written as being foreign born/raised. I think the writers of House believe the audience assumes House is only treating local patients (which actually seems odd if he's as famous in the medical profession as they claim he is), hence the patients end up being American.
Once in a while there is an actor on LOUK I struggle to understand. It has to do with regional dialects and I'm sure a Brit watching a U.S. production with a character from the deep south may be hitting the rewind button as well. ;) But most British accents are 'middle of the road' and easy to understand with an open mind and a tine bit of concentration.