In a way, I know what you mean, often indie films get over-hyped by people who are just so proud of themselves for watching something that isn't a comic book sequel (these people keep Empire magazine in business... ). I'm guessing last years 'big American indie film' would be Juno. But just because they are all American indie films doesn't mean they have anything else in common. It's a bit like saying I saw a French film once and didn't like it so I won't be watching any more!
I'd just like to clarify, I don't dislike or hate American indie films. Hell, I introduced my Film Studies tutor to Slacker back in the 90's. It's just that, every year, there's one in particular (often a comedy) that 'you just have to see' and, invariably, I don't because they don't look good, let alone funny. Those are the films I meant when I used the term "Must See American Indie". I started with Rushmore because that was the first one that I really remember being pushed hard in that way, usually by the same people who tell you that Seinfeld is funny. I guess you could take it back to Pulp Fiction if you wanted to or even Reservoir Dogs or Slacker, but I think that'd be disingenuous.
Pres, I remember seeing Little Miss Sunshine on your list, after reading what you wrote about it, I thought that next time it's on, I may give it a look. The problem is, as I said, I have so many films on the shelves that I've yet to see, that watching something that I'm not up for seeing has been rare over the last few years.