Could Texas form its own alliances?

Yes. A sovereign Texas chooses its own partners, and the most natural and likely relationship is a close, cooperative one with the United States. What changes is that Texas would enter alliances by its own choice, in its own interest, rather than inherit Washington's.

Sovereignty means choosing your own friends

The whole point of independence is that decisions about Texas get made by Texas. Foreign partnerships are no exception. An independent Texas would be free to form the security and diplomatic relationships that serve Texans, the way every sovereign nation does. That is a feature of independence, not a complication of it: the ability to align with partners who share Texas's interests, on terms Texas agrees to, rather than being bound by commitments made in Washington for reasons that may have nothing to do with Texas.

The most likely alliance is with the United States

Start with the obvious. The natural security partner for an independent Texas is the United States: a contiguous neighbor with deep shared interests, an integrated economy, and every reason to want a stable, friendly nation on its southern flank. The most probable path to Texas's strategic security is a mutual-defense arrangement with the United States rather than going it alone. That kind of partnership between allied nations is the norm around the world, and it provides for the most serious contingencies without Texas needing to build for every threat by itself.

Cooperative defense is how the modern world actually works

Shared defense among sovereign allies is ordinary, not exotic. Nations routinely enter mutual-defense pacts and status-of-forces agreements that allow allied militaries to cooperate, share facilities, and coordinate, all without surrendering sovereignty. The United States itself maintains defense relationships and bases with dozens of countries that are emphatically not part of the United States. An independent Texas slotting into that same kind of cooperative arrangement is the well-trodden path, and it is the practical, stabilizing one.

Alliances on Texas's terms, not entangling ones

Texas's stated posture is friendship and honest trade with all, and entangling alliances with none. Those two ideas fit together. Forming alliances by choice, scoped to Texas's actual interests, is the opposite of being entangled in open-ended commitments inherited from someone else. A Texas that picks its partners deliberately keeps control of when and how it cooperates, which is exactly what sovereignty is for.

A position of strength, not dependence

Texas would negotiate alliances from a strong hand. It is a top-ten economy, a major energy producer, and already home to a serious defense base, with more than 200,000 Texans in uniform and the Texas Military Department as a functioning command. Partners would value an alliance with Texas. A confident nation with that much to offer enters partnerships as a desirable ally, not as a dependent seeking shelter.

The bottom line

A sovereign Texas chooses its own alliances, and the most natural and likely is a close, cooperative defense relationship with the United States, structured the same way allied nations partner everywhere. Texas would align by choice and in its own interest, friendship with all and entanglement with none, negotiating from the strength of a top-ten economy with a real defense foundation.