Point of order: Our spending on military bases and what not in other countries (such as Europe [yes, I know it's a continent, not a country]), isn't really to 'defend' them, as much as it is a tool for us to project a massive military force anywhere in the world, as well as prime locations for logistics bases. For example, up until 2008, the nearest level 3 hospital (one that treats extreme wounds and such) was in Rammstein Germany. After that it was in the United States (in 2008 one was completed in Iraq). This base allowed to save hundreds of soldiers, Marines, etc. If they died, it would more than likely cost more than the cost of maintaining those bases.
Now I'm not saying we need to be able to project our power globally anymore, but as long as that is our national policy, those bases serve us more than they do the country their built in.