edit - one thing to keep in mind is that although US expenditure is 2.5 times larger than the EU, much of that historically was spent on weapons rather than troops as it was directed towards trying to bankrupt the USSR by the meta-game of convincing them to play the game of arsenal oneupmanship, while having deeper pockets.
US active serving personnel - 1,369,532 http://en.wikipedia.org/wiki/United_States_Armed_Forces
EU active serving personnel - 1,453,028 http://en.wikipedia.org/wiki/Military_of_the_European_Union
edit - one thing to keep in mind is that although US expenditure is 2.5 times larger than the EU, much of that historically was spent on weapons rather than troops as it was directed towards trying to bankrupt the USSR by the meta-game of convincing them to play the game of arsenal oneupmanship, while having deeper pockets.