Accent
Melanie does, in my opinion one of the best "American accents" of any actor. I think she's definitely better than Hugh Laurie who is really amazing. It's a small but annoying issue having to listen to people like Owen Yeoman(horrendous) and other Brits and Aussies doing horrible accents. Is it that there no American actors good enough who want to do TV? Or is it the novelty of having everyone say, "Oh my god, I can't believe he/she isn't American!" I'm surprised that some of these actors aren't embarrassed. Otherwise you might end up sounding like Paul McCartney in Rocky Raccoon.
I think it gets taken for granted because the average American accent is pretty unremarkable (Dolly Parton and Tony Soprano don't represent the majority). Obviously someone from the UK doesn't find a "British accent" so interesting, but the inflection is much more distinct regardless of region.
Not TV, but Sam Worthington in Avatar...laughable. He sounded like an Aussie trying to do a Boston accent which is presumably what he was going for. If it's some indie film that no one's going to see then whatever, but the fact that James Cameron simply didn't care enough because the movie was going to make a gazillion dollars is a little disappointing. It was a little distracting honestly. Although this is from a guy who didn't care that all Terminator T-800s had Austrian accents.
PS - If any Redcoats bring up Dick Van Dyke-that was like 50 years ago so give it a rest.