Why did many americans criticize the mexican war? how did they see expansion as a threat to american liberties?

Northerners saw the Mexican-American War as a way for the South to try and gain control in the government. The North vs South only existed because it depends on how many of each state there was ( slave or nonslave state).  The North saw slavery as an abomination and that it went against the constitution " all men are created equal".  But South thought that the bible was in their favor because it has passages supporting slavery.  ( sorry this is long)

The right answer would be a