The United States of America needs to become an isolationist country for the time being. There are too many issues in the United States that need to be taken care of for the United States to be worried about other. If they keep helping other instead of themselves, the US will face serous issues.
Here's a good analogy for this: if you saw a another family beating their kids in public (with fists), would you intervene? I would without hesitation call child protective services. If you saw a large man take away a child from a stranger's family, and the family was too weak to stop him, would you step in if you knew you had the power? Sure, you might get beaten, but would you sleep well knowing that you did nothing to help?
Simply replace the "family" from the first example with the Syrian government, "beating" with bombing and gassing, the man with Russia, the second family with Ukraine. We need to be the voice and sometimes the arm of reason in a world full of dictators bent on killing their own people. Not because we are citizens of first world countries, but because we are all people. If you do nothing , don't expect the world to be a better place in your absence.
While the idea of staying out of the business of others is a nice one, it can not always be done. As a super power (for the time being), the United States has a responsibility to help the less fortunate. The U.S. also has an obligation to help out our allies in their time of need as they have done the same for us in the past.