The Republicans seem to worry about a problem from the past

If the net migration between Mexico and the United States is negative, why is the Congress proposing to spend a huge amount of money protecting the border?

I think the real problem is that the proposed protection won't work. If, as we all hope, the economy comes back to full production and full employment, people from poor countries will again want to immigrate.

I think the people in Latin America and the people who help illegals to migrate to the U.S. are smart enough to find other ways than "wetbacking" across the land border between Mexico and the USA. Lots will enter on tourist or other visas and simply stay if they can't find legal access. Others will visit Canada and cross the land border between Canada and the USA. Others will come in via the Gulf of Mexico or the Atlantic or Pacific coasts.