I'm sure they'll think of something. Why did they kill so many citizens of foreign countries they said they went there to help? Them having such big of an army when they are practically isolated geographically, and using that army in wars no one asked for, halfway across the globe, makes absolutely no sense. It's like me having 5 dogs "for protection" when I live alone in the woods, and using those dogs to defend babies 5 villages away and ups, ending up with their candy.

My personal opinion is that no other country is a real threat for them as Europe is. A real threat is dangerous for both physical and intellectual reasons (in this case economical). No one fears a geek or a big dumb ass. China, yes big which means lots of physical force, but still weak economically (see latest Asian stock market, hasn't affected other markets yet). Same for Russia. Yes, islamists, but meh, those are just mean gangs in the end. What else, Latin America, meh, a bunch of poor countries with no common goal or leverage. Africa, the same. Europe on the other hand....

But Europe has had many wars in the past and is done with that, has "learnt its lesson", which means almost no efficient army. Ironically Europe wants what America has, a union that can make us more powerful together. Each European country has its own powerful industries (yes, even PIGS or Eastern Europe), which means a union can take the prize away from the US. That is real leverage.

Europe however is not isolated geographically. That is a curse and a blessing. It can simultaneously be attacked and defended from several directions. Here two interesting things happen. It has no army (a chihuahua is not a guard dog) or military intelligence, but it has a lot of neighbors that have been pissed off at Americans for decades. What do you think is gonna happen when something important is gonna come between Europe and America. No NATO or any other agreement is gonna be worth a damn thing, that's just a signature on a piece or paper.

So, in short, your answer is, for money.