I would argue that monocultures exist because of it's relation to other existing cultures. See:

https://en.wikipedia.org/wiki/Monoculturalism

That said, you are right and monoculturalism is not the right term. It is a political term at best and a charged cultural term in today's racial and cultural environment. It's too late to change the title. Sadly, the rest of my post doesn't mention the term, but the responses don't seem to address anything but the title.