The US and US interests can, at times, be indistinguishable. Isolationism--what you're advocating whether you know it or not--has been proven by history to be very bad for a great many people. Isolationism led to literally hundreds of millions of people needlessly suffering and dying in the 20th c. Fortunately, we had these lessons in hand in the days immediately after WWII, and we were able to somewhat contain Stalin's march across Europe. If you like and respect Western Europe at all, you can thank US interventionism, because without it Italy, France, probably even GB would all have become satellite states of the Soviet bloc in the late 40s and early 50s.

This isn't to say that interventionism is always a good policy. But it helps to keep in mind that in some situations protecting our interests around the globe is good for the citizens whom we're immediately protecting, and is good for us in the long run.

China and Russia currently offer the greatest examples of threats to US interests that could ultimately threaten us or our close allies. Both countries are blatantly violating the modern law we all share that says that countries can't annex territory by force. It is the most essential law of the UN. (Annexation was the catalyst that caused both world wars--Franz Ferdinand was a pretext if anything). At some point, these issues will have to be confronted (hopefully Putin will just implode, but surely China won't). We can hope that diplomacy will prevail, but rule of law is more important than diplomacy, IMO.