Anyone who thinks that multiculturalism allows for population stability is sadly delusional. There needs to be a homogenization and enculturation which frankly hasn't been happening.
Then you have liberals throwing overboard all the traditional moors of our society as quickly as they can in the name of multi-culturalism and tolernace, which just makes it worse.
It's tabboo to say that you believe that immigration should be more heavily favored in nations whose cultures are comparable to ours (which would make freakin' since, but you'll be demonized for it).
*sigh*
America was already homogenized with advances in communications technology (e.g., the telegraph, telephones, TV/radio, computer networks) and shipping/transportation technology (e.g., the automobile, the interstate highways, the airplane).
The problem is that certain elements of our society now seek to break down America using external (e.g., mass illegal immigration from Mexico) and internal (e.g., the diversity push, homosexual agenda) influences.