If solo artists are also allowed here, then my all-time favourite American artist is Elliott Smith. A genius songwriter and a talented musician who sadly died too young. My other favourites are, in no particular order: Wilco (not a big fan of their latest few albums though), Roy Orbison (what a voice!), The Flaming Lips (some great stuff, but sometimes a bit too pretentious and overrated - a poor man's Super Furry Animals), Blondie (catchy tunes + Debbie :redface, Big Star (influenced some of my favourite artists), She & Him (Zooey Deschanel + M.Ward, nice little tunes with a distinctive retro sound), Grandaddy (a bit hit & miss, but their good stuff is definitely worth listening to), The Beach Boys (same as the previous one...), Love (I only know 'Forever Changes' and their self-titled album, but at least those two are great), Tom Petty (& the Heartbreakers... some decent rock&roll tunes), Guns 'n' Roses (not a huge fan, but the guitar solo in 'November Rain' alone makes them worth mentioning here)... ... okay, I suppose that's enough for now.