I repeat..."open border" advocates are not "Americans." Oh, they can be citizens. They can also be citizens of other countries. But they are absolutely not Americans.
Because the concept of a country...every country... is that it has borders. Those borders are definite. They are defended. They are enforced. It is effective borders that make, for instance, Germany different than France, and Italy different from Austria. If it weren't for borders, eventually the languages would merge, individual traditions would fade and the individual country identifications would fade into oblivion.
Those who advocate open borders for the United States of America ... and for the rest of the world if asked ... are those who believe in a World Order or World Government,
They see no value in the United States Constitution, or any other country's founding documents or beliefs, because it is their intention to create a world-wide unit that will be run by an entity populated by those they consider gifted, educated (by their definition) elites that will direct how the rest of the world's population will behave and live.
Should you doubt this, "google" Agenda 21, read all the basic documents and position papers, then check to see the progress that it has made in various countries of the world and get back to me.
Whether our President was Clinton (Bill or Hillary) or Trump matters little to them except as to the degree either of them would present road blocks to the New One World Order. Think of it as the German Reich on steroids.
Consider that the United States of America is almost an ungovernable entity as it now exists, thanks to President Lincoln and the Civil War. And that has nothing to do with slavery. That is based on the fact that the founding fathers realized that a Republic was an effective and responsive form of government only for a limited area or limited population. They full expected that as the colonists expanded into the continent and the population grew that new Republics would be formed to retain the responsive self-rule that they so valued. They full expected those new Republics to create treaties and alliances with the original for the purpose of self-defense, but that each would have a government that would serve the citizens of each respective Republic. Consider this: at the time of the formation of the Republic, each member of the House of Representatives represented 30.000 people. Today, each member of the House represents 720,000 people. To get the same level of responsiveness today, the House would have to consist of over 10,500 people. Does any sane individual really think that your Elected Representative is influenced by what you...or even you and one thousand of your friends...thinks? Does any sane person think that this ratio is even in the ball park of ensuring representative government?
But as bad as this is, consider what would happen with a World Government. Jefferson accurately indicated that eventually government becomes the enemy of individual freedom.
That being so, the question now is whether a sufficient number of our citizens are Americans, and if they are prepared to fight to preserve at least the diluted representative government that we still have.
I don't know the answer...but I suspect that the next decade will reveal the answer.