When we do have colonies on other planets like say Mars or the Moon ?

I've been hearing alot from NASA and even countries like China and the US about proposals for future manned missions and settlements to Mars . If you've read the book The Case for Mars the ideas about colonizing Mars can be done in our lifetime and its only I think a 12 month journey (which theyre researching to cut that time in half) but anyways when we do colonize these other planetary bodies, will these colonies be governed by individual nation state like say the United States or France or Germany or even Japan ? Or will they be like governed by a united body like the United Nations ? Where everyone shares and owns these colonies equally ? And also if we do colonize these planets will we be setting in motion the wheels of mpire and Imperialism again ? Wars fought over colonies and invasions and all that ?