How would Texas secure its border with Mexico?

With more control than it has now, not less. The hard truth Texans already know is that the border is not secure under federal management today. An independent Texas would set its own border and immigration policy, direct its own forces to the line, and answer to the people who actually live with the consequences, instead of to officials a continent away.

Border security is already largely a Texas effort

The state is not starting from zero. Texas already funds and runs major border operations with its own money and its own people. The Texas Department of Public Safety, the Texas Rangers, the Texas Military Department, and the Texas Highway Patrol are on the river right now. The state already appropriates its own budget for border security on top of whatever the federal government does, precisely because Texans concluded that Washington was not getting the job done. The institutions, the personnel, and the will already exist inside Texas.

Independence removes the official a continent away

Today, the most important decisions about the Texas-Mexico border, how it is enforced, who crosses, what the policy is, are made in Washington by people who do not live near it and do not answer to Texans for the results. That is the core dysfunction. Independence ends it. A sovereign Texas would own its border policy completely. It could decide its own enforcement posture, its own ports-of-entry rules, and its own immigration system, calibrated to Texas's needs rather than to a federal compromise written for fifty states with conflicting interests.

A secure border and a working crossing are not opposites

Securing the border does not mean sealing it. The Texas-Mexico relationship is one of the largest trade relationships on Earth, with two-way commerce that runs into the hundreds of billions of dollars a year, and more than a million lawful crossings happen on the southern border every single day for work and family and trade. An independent Texas has every incentive to keep lawful trade and travel flowing while stopping what is unlawful. Secure and open are settings on the same dial, and Texas would finally be the one turning it.

This is a neighbor relationship Texas would manage directly

After independence, Texas and Mexico would be two sovereign neighbors sharing a border, the most ordinary arrangement in the world. Neighboring nations manage shared borders through their own agreements all the time, on crossings, on commerce, on cooperation against the cartels that threaten both sides. Texas would deal with Mexico directly, as an equal, with Texas interests represented by Texans for the first time, rather than filtered through federal negotiators in distant Washington who weigh Texas concerns against everyone else's.

Defense and law enforcement, scoped to the real threat

The serious security challenge on the border is not a conventional army. It is the cartels and the criminal networks, and the risk of bad actors exploiting the line. That is a mission for capable law enforcement backed by the Texas Military Department, working with whatever cooperation Texas negotiates with both Mexico and the United States. It is exactly the kind of practical, layered security a sovereign Texas is built to provide, and the kind it already provides every day on a smaller scale.

The bottom line

An independent Texas secures its border the way it already largely does, with its own forces and its own funding, but with the one piece that has always been missing: full control. The decisions would be made in Texas, by Texans, for Texas, instead of by Washington. That is the change, and it is the whole point.