Part of the problem is that it can be difficult to identify the Einsteins early enough to give them the visa when it would still matter. However, I don't think it would be difficult for an established scientist to gain US residency even under the current miserable system. Top athletes, entertainers, business people, scientists, and so forth inhabit a completely different universe.
As for "running out of land"... that's actually a little ambiguous. California could probably triple in population, and we'd still have some rural-ish areas in the extreme north. Japan, because of the density of its cities, actually preserved its rural character in some areas, and this is a country with a population density of 337.1/km2! In other ways, California has already "run out" of land. Ever drive from Orange county down to Tijuana? With the exception of a military base, it's basically sprawl all the way down. I suppose we could increase the coastal population by building high density housing on the coast...
As for "running out of land"... that's actually a little ambiguous. California could probably triple in population, and we'd still have some rural-ish areas in the extreme north. Japan, because of the density of its cities, actually preserved its rural character in some areas, and this is a country with a population density of 337.1/km2! In other ways, California has already "run out" of land. Ever drive from Orange county down to Tijuana? With the exception of a military base, it's basically sprawl all the way down. I suppose we could increase the coastal population by building high density housing on the coast...