The Department of Defense is 99.9% offense, 0.1% defense. You can use the argument that the best defense is a good offense, but that doesn't really excuse the number of (largely unprovoked) attacks on and occupation of other sovereign nations.
0.1% defense in terms of actions, but not in terms of capabilities. It's just that attacks on the US are very rare, because it's so capable of defense.
US military dominance is an ever present defense for nations around the world who would otherwise be harrassed or attacked by aggressive neighbors. US military involvement in the Middle East doesn't change that.
Of course you can argue we shouldn't be involved in the Middle East, and there are some reasons to think we shouldn't be, but we can agree on that point and still believe the US should have the world's dominant military.
