Incorrect. You are part of the world, so you will be influenced by it, and you will yourself exert influence upon. Isolationism cannot work.
I'm not talking about total isolationism. I believe in proactivity when it comes to helping other people who aren't being left alone as well. I still have a strong belief in the "Golden Rule" if you will. The idea that we should "do unto others" as we would have done to us. That means helping the oppressed, slaves, the sick, the gay, etc.. Situations when people are being intruded upon, and not hurting anyone with their existence.
I don't believe in sticking my fingers everywhere though, meddling in all manner of political affairs, expanding borders, or seeking out "new vassals" to advance some preconception of what "world culture" should be. There is no world culture. The sooner we respect the many types of people and cultures though, then we might come close to a global understanding of....something.
edit: This is a bit off topic, I think. But I said my piece.