@JTT,
We were given one year to get out, and at the end the Philippine government accepted the keys and said that we had fulfilled our agreement to get out. We kept our end of the deal, the Philippine government accepted that we were done.
If the Philippine government changes their mind and can prove that the area is a toxic mess, that we caused it, then America will revisit the issue. Failing that, having honored our former friends wishes to end the friendship, we are under no obligation to investigate or pay for the problems in a country that we no longer have any ties too.