Advanced Space capabilities are in all likelihood coming rather soon, with SpaceX’s next generation rockets at the forefront. However, exploration of how a colony will fit into the global stage has only been explored by fiction authors thus-far and not decision - makers.
Mars does not need a fixed government
A colony on Mars would be too small to have a government.
Anarchy
People on Mars could live their lives just as well, if not better, without a large, formal government ruling over them. Rather, Martian society should encourage common stewardship and a rejection of capitalist principles.
With companies becoming arguably more influential players on the global stage than some nation-states, it is perceivable that Mars will be under the rule of, for example, Elon Musk's SpaceX.