Maybe it would be better to explain why the US would be better off with a declining population?
Because that’s the status quo if immigration were to be cut off.
On top of that, US economy depends way more deeply on undocumented or migrant labor than most people realize. Good luck getting strawberries or a new roof on your house without immigrants.
I say the US is uniquely well-adjusted to integrating immigrants compared to most other countries and should effectively make its borders open with an instant/automatic documentation process. Get immigrants and migrants out of the under the table cash economy and make them citizens or something close to it ASAP.
Of course Republicans act like immigrants are a bunch of freeloaders despite the US literally denying basic needs like healthcare to you unless your employer gives it to you. Even the most idyllic interpretation of this American Dream involves very hard work. You literally can’t survive in the US without work, the US system really doesn’t allow freeloading. There’s no such thing as dawdling around in free college forever or collecting inflated welfare checks and living large off the government’s dime in the US.
Alternatively, perhaps we should explain why immigration should be disallowed in the status quo where the occupants of America stole the land.
My ancestors stole this land from its precious inhabitants, who am I to say no one else is welcome?