Usually in a strict / legal sense "migration" / "immigration" refers to people migrating permanently, with no plans to return, and becoming permanent residents / citizens etc. That is somewhat difficult for Chinese folks to the USA due to various numerical caps on visas by origin country.
There aren't any regulatory / numerical caps on Chinese folks studying or visiting the USA though, as long as they can get into their college, pay the fees, satisfy the various embassy / CBP people that they are temporary / non-immigrant visitors, they are free to come. In practice, the barriers are financial, logistical and linguistic.