The greatest chance to do something came in the wake of 9-11, when GW Bush could have gotten Congress to throw out the entire awful U.S. Immigration law and start with a blank sheet. He also could have seriously reduced illegal immigration.
Instead he padded into a mosque in his socks, stammered nonsense about Islam and peace, allowed Muslim immigration to soar, renewed "TPS" amnesties for Central American illegals, left the border open, and even tried to shove even more amnesty down our throats ("See you at the signing").
This is also correct.