Demographics (race) is what matters when it comes to nations. That doesn’t mean that a lot of other stuff doesn’t matter, but demographics matter most. A lot of things matter when it comes to movies, but the story matters most. Look at the image below.
It is an accurate statement to say that in 25 years the orange and the red states will no longer be American (in fact, some of them are already not American). This is how territory is lost, and once lost it is very very difficult to get back. Will those states still be under the jurisdiction of the United States Government, yes, will there still be courts and taxes and roads, yes, but they won’t be American. Let me show you another map.
(It’s not quite to scale, but close enough to get the idea)
The roman empire controlled many separate nations. Although they were all part of Rome, and under the control of Rome, they had different peoples (races) with vastly different beliefs and customs.
One of the major differences between the Roman empire and what will become known as the American Empire, is the way in which they formed. The Roman empire was formed by a small nation overtaking all of it’s neighbors, and spreading through conquest. The American Empire is forming in reverse, it is a large nation that has been invaded by many of its neighbors. As those peoples who come to America (from near and far) continue to grow in size, they will develop nations within the boundaries of traditional America. They will still be ruled by Washington, just as Rome ruled the farthest reaches of its empire, but they will not be American.
There are several ways to prevent this from happening, but the most humane, is mass deportations.