The point is that the reason the americans and the poles are "entitled" to their respective countries is not because of some deep relationship with the land, it's because the political mythology we have created for our times necessitates borders and independent countries. And so we divide ourselves into different states, not primarily based on history or tradition or whatever it is you think entitles the poles to poland or the americans to the US, but based on whatever people can get to happen.
So, what we saw from the "UN action" was really a transfer of power of that land from the British (are you OK with the British controlling that land, or do they not have a "right" either?) to the newly formed Israeli government.