At least until the invention of FTL travel.
When we think about space travel we commonly think of the societies on other planets as being intrinsically tied to Earth in some way, be they politically, socially or economically dependent - forming a federation or confederation of some sort.
But we commonly overlook the unprecedented amount of -ISOLATION- any settlement on another world will experience. Certainly, within the solar system the EM communication delay will range from a few minutes to a few hours, making Earth's influence relatively available, but that's assuming the settlers will be wanting anything to do with Earth in the first place.
Assuming Earth's culture becomes more globalized and homogenized as it has been going lately, there will be a push in the opposite direction by millions of people seeking to lead some other kind of existence than the one Earth has in store for them. I see the early future of space colonization as one of nation-state settlements, private corporate states, ideological communes, racial supremists and kooky cults all competing and vying for territory. Not to mention the genetic speciation that different groups of humans will begin to exhibit in their isolation within a matter of generations - be they speciating by natural processes, genetic engineering or their relationship with technology.
Until FTL technology comes into play, it will be very hard for any one culture to maintain hegemony and human-owned space will resemble more a patchwork of groups than a cohesive whole.