The diplomatic view may be that Texans were invited by the Chickasaw Nation. If you read the Texas Declaration of Secession you will see a large complaint of the U.S. Government for failing to protect the Texas frontier from Indian attacks. It was an intolerable breach of faith following the annexation in 1846.

And the Civilized Tribes were not as proficient at fighting Commanches-Kiowas as the Texans.

Given the current border situation, this annexation arrangement still does not work.