I agree that we can’t save them from the Muslims with our military. That they must do themselves.
However, we must understand how and why we are there. Communism was a large and growing threat after WWII. General George Patton said that we would have to fight them sooner or later so we might as well fight them while we are there and still mobilized for battle. Truman disagreed and Patton died after a strange accident in Europe.
We allowed Russia to stay in Eastern Europe after they agreed to leave after 3 months. They reneged and we formed NATO with Western Europe.
Most of the Eastern Hemisphere was wasted after WWII and we were the biggest kid on the block. We could have taken over the world were we so inclined. We weren’t but we did maintain a large enough military to protect ourselves against the expansionism of the USSR. We did that in Korea and South Vietnam. We have been protecting everybody else ever since and they have grown to expect it. Personally, I think it is cheaper for us to protect them than to allow them to be taken over by the USSR and then have to fight them after that. However, we may still have to do that after the Muslims take over.
At the time the European countries maintained their own credible military forces. Now they run out of ammunition trying beat Libya. Why should we take up the slack when they refuse to?