Answer:
To gain natural resources.
Step-by-step explanation:
Beside land, the United States gain access to more natural resources from expansion. There are a lot of natural resources such timber, coal, oil and more land for agriculture etc. Shed of American blood on American soil and unification of Texas to the United States are the two reasons due to which the United States of America going into the war with Mexico. More burden on economy is the reason that America not to go to war with Mexico in the 1800's.