Where is the line between Texas and Mexico? It’s a question that captivated Americans in 1846 but one that most of us thought was resolved definitively in the Treaty of Guadalupe Hidalgo two years later. Instead, here in 2024, the Biden administration is conducting a bold experiment in postnationalism by reducing border enforcement to a series of checkpoints and pinky swears as it ushers in a record number of illegal immigrants from around the world. It is a slow-motion crisis that has, finally, become a top concern in voters’ minds.  But is the federal government’s failure to act a prelude to civil war? It’s not likely despite overheated rhetoric in the press. President Joe Biden’s determination to roll back Trump-era restrictions meant that illegal crossings began to increase immediately once he took office. Customs and...