What is going to happen, you ask. Well, one look at world history will show you that no country with a diverse population of different races, languages, and religion has long survived.
Countries don’t naturally form with a diverse population, and when in the past they’ve occurred it’s usually been as a result of armed conquest. These unnaturally formed countries have either melded together into a single population made up of one mixed race with one language and one religion or they’ve come apart, and they’ve usually come apart with extreme violence. The longer these diverse populations were forced to coexist with one another without mixing and becoming one, the more the hatred grew among them and the more violently they broke apart, but break apart they did, or genocide has settled the issue once and for all.
The Romans lasted for hundreds of years.