Bottom line: So-called real Americans are screwing up America. Maybe they should leave, so that we can replace them with new and better ones: newcomers who are more appreciative of what the United States has to offer, more ambitious for themselves and their children, and more willing to sacrifice for the future. In other words, just the kind of people we used to be — when “we” had just come off the boat.

O.K., so I’m jesting about deporting “real Americans” en masse. (Who would take them in, anyway?) But then the threat of mass deportations has been no joke with this administration.

On Thursday, the Department of Homeland Security seemed prepared to extend an Obama administration program known as Deferred Action for Childhood Arrivals, or DACA, which allows the children of illegal immigrants — some 800,000 people in all — to continue to study and work in the United States. The decision would have reversed one of Donald Trump’s ugly campaign threats to deport these kids, whose only crime was to have been brought to the United States by their parents.

Yet the administration is still committed to deporting their parents, and on Friday the D.H.S. announced that even DACA remains under review — another cruel twist for young immigrants wondering if they’ll be sent back to “home” countries they hardly ever knew, and whose language they might barely even speak.

Beyond the inhumanity of toying with people’s lives this way, there’s also the shortsightedness of it. We do not usually find happiness by driving away those who would love us. Businesses do not often prosper by firing their better employees and discouraging job applications. So how does America become great again by berating and evicting its most energetic, enterprising, law-abiding, job-creating, idea-generating, self-multiplying and God-fearing people?

Because I’m the child of immigrants and grew up abroad, I have always thought of the United States as a country that belongs first to its newcomers — the people who strain hardest to become a part of it because they realize that it’s precious; and who do the most to remake it so that our ideas, and our appeal, may stay fresh.

That used to be a cliché, but in the Age of Trump it needs to be explained all over again. We’re a country of immigrants — by and for them, too. Americans who don’t get it should get out.