I just see that he's buried in allegations of corruption.

But then...

So is Trump.
So is Putin.
So is Netanyahu.
So were Dilma and Lula, until Dilma was impeached.
Likewise Angela Merkel until she just got re-elected last week. I wonder how that is possible!

In the case of Duterte, I get the impression the allegations are unmistakeably true, and there is pressure for him to resign. But I don't get the impression from the news that there is any movement in the U.S. to militarily remove him.
There's plenty of other stuff on the table, a potential war with Kim Jong Un, a potential military action to invade or bomb Iran to keep them from nuclear weapons, by either the U.S., Israel, or both combined.
Less likely, a military conflict, or trade war, with China, or with Russia who intervened in our 2016 election, and has made moves toward doing the same in the Nov 2018 U.S. election. Not to mention Russia poisoning former Russian agents in the U.K.

So I'd say the plate is pretty full right now for the U.S.
And since the U.S. military is currently so crippled by 8 years of Obama "sequestration" slashing the military's budget, to the point that only 40% of our air force and navy are ready for combat, I have a feeling Trump would like to wait at least a year or two till our military is much more combat ready before taking any large-scale military intervention in the near future.

So with all of that going on, the Phillipines are pretty far down the list.