[nomailing]

Yes. Also, if several nations have colonies on Mars, I would assume that they would all claim independence roughly at the same time and soon after would form some kind of pan-martian government.

It just makes more sense to increase collaborations between colonies if you are so far away from earth. If there would be a US colony on Mars and a Chinese colony on Mars, these people would probably have more interactions with each other than with any person or nation on earth. There are huge advantages of exchange of goods between colonies, so that not every colony has to produce every special item or mine every kind of resource.