Foreign student enrollment of about 20% or 25% sounds normal, at 40% or 50% this is unusual and suggests American educational resources are being used to a disproportionate degree in a way that is not putting American students first.
40 percent or close to 40% Universities are Carnegie Mellon, Columbia, John Hopkins
35% or close to that Universities are NYU, Rochester
30% or close to that Universities are Caltech Chicago, Harvard and Penn
Close to 25% are Duke, Cornell and Rice, Stanford, Princeton, Yale and Northwestern, Georgia Tech
Close to 20% are Dartmouth, Georgetown, Emory, UC Berkeley and Davis,Michigan