An insight into your fear and ignorance might help others.
There would be no America you love without immigration. People back then, knew that, it wasn't a mistake, it was intentional.
A billion people is a massive migration, that just isn't happening, it's fairy tale nonsense to frighten children. And if it did happen, the best way to manage it is rationally and compassionately, not emotionally with fear. That's what happening in your country, immigration has been weaponised, been used as a topic to frighten you as it very evidently does. You see immigration as the end of your world.
When you are scared, and you are very scared, you are easier to control. Why would anyone want to control you? A very wealthy minority want to control you to protect and extend their power. It is always about resources, this minority want the best of everything and only want to share a little of it with their supporters. They are just playing out their survival strategy, a primitive and short sighted one.
What's motivating them is something very old and evil, greed. We are all selfish, ruthless and greedy to some degree, a minority are very selfish, ruthless and greedy and a reliable measure of that is how much wealth they have accumulated so far.
Immigration is not something to be scared of. It is something else to manage. Being ruled by the most selfish, ruthless and greedy is something to be scared of. Greed is like a cancer, all it wants to do is consume and it will until it kills its host. Immigration is being used to frighten you to enable greed to kill your country, it's not intentional, it's just human nature playing out.
What do I want? For you to show some American courage and not kneel to lesser men, ruled by a fear of not having enough.