I don't think Texas was purchased. It declared itself an independent republic after Santa Anna's defeat at the battle of San Jacinto. Texas is the only state that was once a country.actually that was Roosevelt's message to America in 1910. Roosevelt, a Republican sought to drive out from politics and American democracy corporate financial influence. Up until Roosevelt the dynamics in America was exactly as it is today. The Rich were getting richer and the back bone of America, it's workers were struggling taking on medevil European similarities. America was a nation of surfs, the old and poor dying in the streets, a lot of those conditions would last for another 25 years until the Social Security Act.
The purpose of Government is to protect the rights of the people. The rights established by the U.S Constitution and to ensure the distribution of justice and up hold the laws of a free democracy.
There aren't but 15 States in America on lands that weren't allocated, proportioned and determined by the U.S Government. Two of those was purchased by the U.S Government after formation of the Nation, Texas and Alaska which were purchased from Mexico and Russia.
Texas wasn't involved in the Gadsden purchase, if that's what you were referring to.
The constitution is the supreme law of the land that was supposed to protect us from government.