Person, Lawrence. "Huddled Masses"
Divergence: 1984 CE
What if: Walter Mondale beat Ronald Reagan in the 1984 election, and Nicaragua took the opportunity to export revolution.
Summary: In 1989, while US forces intervene in the Mexican civil war, refugees overwhelm the Immigration and Naturalization Service in Houston.
Published: In Alternate Presidents (ed. Mike Resnick), q.v.