well i'd say it depends.
as far as huge musical acts go--rolling stones, beatles, zeppelin, U2, Radiohead etc--I'd say Europe had the market cornered on great rockstars. (there are exceptions - Nirvana, REM, Pearl Jam....)
in punk, i'd say the same--Sham69, The Clash, The Business, hell all oi!, Crass, SLF, the Pogues....
in indie rock, it's all the USA. the VU, Glen Branca, Sonic Youth, Mudhoney, Black Flag, Dischord Records, and more recent stuff like the Liars, Lightning Bolt, Les Savy Fav, etc etc etc