From my understanding... which could be wrong... the US is now behind CERN because of our lack of funding. I was in a seminar course on antimatter by a US physicist when someone began asking questions about recent developments at CERN, and the guy totally went green with envy, before trying to downplay their results. And of course one of the problems is that we are not in a position to doublecheck their results, nor produce original results of our own.
Most particle physics experiments are large international collaborations. Extensive participation by US physicists on experiments at CERN, and European physicists on experiments at Fermilab/SLAC, (and Asian physicists at both) are more the rule than the exception.