The Biden administration announced Thursday it will sharply step up the expulsion of migrants from Cuba, Nicaragua and Haiti who show up illegally at the U.S.-Mexico border. The administration also unveiled a new program to allow as many as 30,000 migrants from those countries to live and work in the U.S. If they want to immigrate legally, migrants from the three countries — as well as Venezuelans, for whom there’s been a similar program in place since October — need to have an eligible sponsor in the United States willing to provide financial and other support. The migrants and their sponsors…