Remember how you guys annexed Texas from above mentioned Mexico?
What you guys, do you speak about? The United States had no part in Texas breaking from Mexico. It was a revolution of settlers and Mexican citizens living in Texas. This occured after Santa Anna declared himself Dictator of Mexico. The result was the establishment of The Republic of Texas. Which joined the United States of it's own free will some nine years later.
THE DECLARATION OF CAUSES
"Whereas, General Antonio Lopez de Santa Anna, and other military chieftains, have, by force of arms overthrown the federal institutions of Mexico, and dissolved the social compact which existed between Texas and the other members of the Mexican confederacy; now the good people of Texas, availing themselves of their natural rights, Solemnly Declare:”
"That they have taken up arms in defence of their rights and liberties, which were threatened by the encroachments of military despots, and in defence of the republican principles of the federal constitution of Mexico, 1824.”
"That Texas is no longer morally or civilly bound by the compact of union; yet, stimulated by the generosity and sympathy common to free people, they offer their support and assistance to such members of the Mexican confederacy as will take up arms against military despotism.”
"That they hold it to be their right during the disorganization of the federal system, and the reign of despotism, to withdraw from the union, and to establish an independent government."
This document was created in justification of the Texan actions which were to follow. The Declaration of Causes was to convince the Federalists that the Texans only desired to preserve the Mexican Constitution of 1824 and to justify the Texan actions to the rest of the world.