Your quote is circular.
There is base because US want so, not more not less.
As the only military Superpower I think it makes sense.
Are you looking for a different kind of argument(i.e ethical or biblical)?
The answer of "WFT it wants to" isn't very enlightening, even from a realpolitik perspective.
Why is the US occupying part of Syria? Why is the US involved in the middle east at all?
Because it has economic or geopolitical interests(or both) in there and because it can. Even a tiny country(i.e Belarus, North Korea) can play a role in a big conflict so why would U.S give up influence?
If the U.S doesn't show up Russia or China takes the whole cake(influence wise).
Not to mention the 9/11 thing. Imagine the whole Syria ruled by Al-Qaeda or IS
Like it or not America's isolationism ended after WWII began and I think overall it was a good thing for the whole world(at least a big part of it).
It sounds like you have no idea what those nebulous reasons are.