Depends...
Actually, most of the music I listen to is from Scandinavia, but I'll exclude them for political research.
America has some better, faster/heavier music, but we tend to have too many bad bands and genre's floating around all over the place. [American fave's: GWAR, White/Rob Zombie, Megadeth]
England seems to have more of the major bands in the more basic genre's, but they're good bands are fucking excellent. [England's fave's: Iron Maiden, Sex Pistols, Judas Priest]
So if you're pitting the best of America with the best of England, my vote's for America, but if you're talking about bands in general, England wins because they don't have country and thousands of cookie-monster vocal bands.