Steven Universe and colonialism

Steven Universe is often praised for its diverse cast of characters and positive depictions of LGBT rights and issues. However, I feel one central theme has been mostly been ignored throughout analysis of the show, aspects of colonialism present via the Gem Homeworld's invasion of various planets, including Earth. The characters on the show often mention Earth as a Gem colony yet I feel that there is a lack in addressing the ramifications of what this means. Historically there are many examples of cultural influence and knowledge imparted by colonists to the inhabitants of their colonies, (The French and Haiti, England and India, and others for example). Yet, there seems to be little impact of Gem colonialization on the Earth or the human inhabitants, most of which seem to be totally unaware of Gems. I think there is some interesting stuff to explore in this unexamined theme.