Our stated reason for continuing our wars in Iraq and Afghanistan is that we need to finish what we started: we can't leave with things worse than they were when we arrived. We need to establish stable governments in these countries.
But the United States' government has shown that it is not able to govern at home. Congress can't cooperate to pass necessary spending legislation. Corruption is rampant; corporations have control of their own regulators, and have successfully dismantled much necessary regulation. Respect for law is at an all-time low because Congress keeps passing arbitrary and capricious laws that are not in the public interest.
Until we can get our own house in order, we have no business telling foreigners how to run their countries.