We won't but we should.
We should take everyone that can get here - everytime. It's like tryouts - want to be an American? Get here.
A person that chooses to leave their country for the idea of another knowing full well the arduous journey ahead and the struggles all immigrants face everywhere - all so they can maybe have a life they like, deserves to be an American... if they can get here.
That's the test - or so it should be.
We are the descendants of those that said "f*ck this" - we should want everyone with that mentality to come here, always.
That mentality is what being an American is.
...plus China and India have a billion people MORE than us - 100 million immigrants wouldn't catch us up. Most people do have kids tho - even if your a Trumper you should understand that not all of the immigrant children will continue to require government assistance - most will go get jobs, go to school, start families and all of that creates wealth and prosperity.
Even if it takes 2 generations for the US to recoup the expenses incurred providing for the 1st generation of immigrants or refugees - the country still wins exponentially.
Nothing is more valuable than people.