Why did Americans from the south and west WANT to go to war with Mexico?

The reason Americans from the south and west wanted to go to war with Mexico is because they wanted to expand their territory of the United States. This war was basically a battle for land, or territory. Mexico was fighting to keep their land, while the U. S fought to retain the land from them which is not Texas and more of Mexico's northern lands. The U. S. Congress approved the declaration of war on May 13, 1846 with the majority voted for the war to be taken place. They claimed that Mexico crossed the boundaries of the United States and is invading their territory. Another reason why the Americans wanted to go to war with Mexico is to get more land for slavery. They wanted to get more land so they could get more slaves and show their political power upon them. Because Mexico was in a difficult time, it was hard for them to win the war to keep their land, so they gave up and allowed the U. S to take their land