Um, unless you are a Native American, your people immigrated from somewhere.
My father was an immigrant, my wife is an immigrant.
Fact is, we could absorb millions of people with no problem. Every consumer is also a producer, so immigrants are good for the economy.
The problem the Global North (the US, Canada, Western Europe, and Japan) faces is that it isn't reproducing at replacement rates. The Global South (Latin America, the Middle East, Africa, and Asia) has a surplus population.
Nature abhors a vacuum.
Trump's not just going after illegal immigrants, he's going after legal ones. He's going after naturalized citizens.