I'm split here. I was born and grew up in the UK, and am here again now, but most of my best years listening to music was when I lived in the US. It's remarkable how a relatively small country like the UK has produced imo at least 50% of the greatest rock acts in history, but then would any of them have even existed if it wasn't for primarily USA based origin music? (jazz, blues, gospel, soul, C&W etc) So probably as it's a poll question just about the 70's, then I'll say UK, but if it was the 60's, then it would be the USA, no contest, you look at the sheer number of all time great acts the US produced in the 60's, it's just a phenomenal number, though I guess the 3 biggest (Beatles, Stones, The Who) were all Brits.