Coming from a center-left POV (though the r/l framing makes little sense any more) I too disagree with the way Trump is pulling the troops out of Syria, even though I agree we should reduce our involvement there. As I heard one anonymous adviser put it, "jumping out the window of the 40th floor and taking the elevator both get you to the ground."
As to the unending nature of wars in Afghanistan and elsewhere, and the ongoing existence of ~800 military bases outside the USA, I think it's important to think of the costs and benefits -- especially benefits that may not be evenly distributed, or that are not "first order" benefits.
For example, when American taxpayers spend money on the military, that money goes somewhere. That is how money works. We are buying equipment, vehicles, weapons, medical supplies, and fuel -- lots of fuel -- all from government contractors. Many of these are public companies that index investors here at the MMM forums are likely invested in. Those corporations pay American workers to manufacture stuff so that we can consume it in military activities. When a bomb gets dropped from a drone somewhere, profit is realized for an American company. Munitions are expensive single-use consumer goods.
When we use arms sales to motivate allies or antagonists, we are making an economic play, not just a military one.
Much of the damage we cause in places like Iraq then needs to get rebuilt, using US dollars. Who receives those dollars? American contractors like Halliburton et al.
So it's not as simple as saying, "let's pull out of these places and stop spending money." It would literally cost too many jobs if we stopped these wars. Too many Congressmen have military-involved industry in their districts to let it happen. Would it break the economy? Heck no -- we could spend those dollars on infrastructure, education, the Arts -- all better ways to spend it than manufacturing bombs.
The argument goes that the post-WWII world order has been ensured by the USA's military might around the world. If that's true, we and the rest of the world (the West, anyway) are reaping the benefits in peace and prosperity. If we want to withdraw, what or who replaces us? Is there an alternative aside from letting Russia and China inhabit the power vacuum such a turn inward would create?