I'm not convinced that the price of maintaining that large of a presence is offset by the amount of trade we would lose without them, because I just don't see what trade we would be losing in the first place. It isn't like the lack of US naval bases (If we are required by treaty to have bases in Japan then so be it, but that's just part of the whole) would cause China to cut off trade - they can't afford it any more than we can. And it's not like, without nearby bases, we would be helpless. I live about an hours drive from Whitman Airforce Base, and the stealth bombers there have the capacity to fly missions to the middle east from here in the middle of the country. 

And what would be the purpose of our system of alliances if our allies need our presence to be effective on even a basic level? I'm sure, in the rare event of a legitimate war between major powers, that our allied countries would be perfectly fine with our setting up temporary bases. It wouldn't be an ideal situation I grant you, but the unlikelihood of a war between major powers in the modern world seems to offset this.

If Iraq taught us one thing, it is the price of maintaining an Empire shouldn't be shrugged off. That is realism - we can't get caught up in all the emotions of being top dog and forget to look after our own health. I'm not saying "Fuck it, disband the military and get out the bongo drums." I get that we need to be able to defend our interests, but we can't take that so far that we become overextended. Especially when it isn't 1955 and our domestic situation is declining.