There are not unlimited slots in universities. Once they fill up no more people can go. ....
If a university "fills up" the university expands. In any case, "slots" are based on competitiveness. That's why American universities are the best in the world.
Yes, they can expand. But that will be a help for the class two years down the road. And by then the population will be even higher. because this wave of immigration is not ending.
And competition does not help the American student, if he loses.
The goal of American Immigration Policy should be to advance the interests of American citizens.
Increasing competition for them is not helping them.