dude... i voted USA for obvious reasons.
but as far as i'm concerned there are ZERO contenders other than the US and UK.
its a ridiculous question if one includes those two nations head to head.
No contest between the two.
Its like two identical supermen getting into a fight to the death, and they both land a fatal punch on the first hit.
in fact when it comes to classic rock there really isnt a USA or a UK... the USA and the UK just meld together to form something better known as
*---EPIC---*