But take America and England. America never actually lived at England's place! He was often left in his own country with England coming to visit him now and again! Now look at the distance between America and England on the map. There's a damn good reason why America didn't actually live at England's - he's far away!
So now let's look at colonies in Latin America, Africa, Asia and the Pacific. Again, they're a damn good distance away from Spain, Netherlands, England, France and Portugal. (well, with perhaps the exception of Spain and the North African countries). So maybe, just maybe, your colonised oc nation was not some chibi desu thing living in their coloniser's house??? Maybe they just stayed where they were and got visited instead.
Take Philippines for example. Philippines was governed by Spain via Mexico, who was New Spain. This was because the distance between New Spain and Philippines was smaller than Spain and Philippines, making for a rather convenient trade route to Asia. So if anything, Spain would not only have left Philippines in his/her own homeland, but New Spain probably did a lot more of the visiting!
And with England and all his colonies. Do you seriously think he crammed all his colonies into one house? I don't think so. They all needed managing, but that can be done in the places they represent. He'd have had people assigned to deal with them, the way his own nation had its own leader and so on.
I'm just sick of seeing APH OCs that were once colonies depicted as little kawaiified maid-kun/chan's in their coloniser's house. Seriously. 8I