You could extend the argument to intra-national competition. What if instead of competing with each other, we were all aligned towards common goals. Unfortunately and sadly, such is human nature that we are hardly motivated by much else than one-upping each other.
I think you basically identified the root cause of the issue. We are, unfortunately, only slightly evolved chimpanzees; We would gladly form groups to fight another group when bananas grow sparse.
Had we evolved from bonobos, things might have been different.
This is true. Instead of competing against each other, we -I mean all nations and individuals - should do something to support efforts so that humans can some day escape this planet. Earth is not habitable forever.
There are many very likely scenarios making this planet unhabitable: asteroid, black hole coming near solar system and moving planet distances, gamma ray burst, any deviation in sun's radiation. All these are clearly possible and likely to happen in the long run.
