That's true. When there was trouble in the Balkans, Europe was uncapable of dealing with it and had to call Uncle Sam. On the other hand, the EU is good at using its economic muscle. For instance, in 2004 the EU expanded its territory by over 20% without firing a single shot ;-)
http://en.wikipedia.org/wiki/2004_enlargement_of_the_Europea...
To cut a long story short: sometimes (relative) economic prosperity is more persuasive than military action.