Lush I think your points are pretty much correct on the surface.
However you are looking at pretty mainstream music I'm sure there is a whole undercurrent of bands in the States doing the type of music you mention.
From the top of my head you could throw in Fountains Of Wayne,Ryan Adams,Sufjan Stevens,Wilco,LCD Soundsystem,Flaming Lips,REM and countless others..... all bands that don't quite fit your theory.
You can continue with the whole Alt-country thing and power pop genres right through to the post-rock experimental sounds of Tortoise and God Speed You Black Emperor.
I think America is just as vibrant as the UK in the genres you mention,you just need to scratch the surface.
However you are looking at pretty mainstream music I'm sure there is a whole undercurrent of bands in the States doing the type of music you mention.
From the top of my head you could throw in Fountains Of Wayne,Ryan Adams,Sufjan Stevens,Wilco,LCD Soundsystem,Flaming Lips,REM and countless others..... all bands that don't quite fit your theory.
You can continue with the whole Alt-country thing and power pop genres right through to the post-rock experimental sounds of Tortoise and God Speed You Black Emperor.
I think America is just as vibrant as the UK in the genres you mention,you just need to scratch the surface.