Going to war with Mexico was Justified

Can’t decide if the United States going to war with Mexico was justified or not justified? It can be a struggle to decide. Mexico won its independence from Spain in the nineteenth century. Spain controlled most of Central America. Due to the extremely low population for such territorial extension, Mexico relaxed its immigration policies, as a result, allowing American settlers to help populate the northern territories. Their conditions to settle were self-explanatory. Now what do think? The United States was justified in going to war with Mexico. The United States was justified in going to war with Mexico because, of the Manifest Destiny, Mexico robbed the United States citizens, and the U.S. wanted to extend slavery and land.
One reason the Mexican war was justified was because of the Manifest Destiny. (Doc A) When we’re welcoming Mexicans into the Texas territory, they’re keeping the U.S. from expanding. America needs land because of our massive population. Mexico’s government is so deprived that they can’t keep California. If Mexico can’t afford California, how will they even afford Texas? America will eventually have California, but that’s not enough for our evolution population. This evidence shows the U.S. was justified in going to war because Mexico can’t control the land they already have; America has more population than Mexico, the U.S. should have more land.
A second reason the Mexican War was justified was an invasion that Mexico has passed the boundary of the U.S. (Doc B) James Polk, an American Political wrote to the Senate and House of Representatives that was a war message from the President. James informed the Senate & House of Representatives to order an efficient military to take position on the Rio Grande to meet a threatened invasion of Texas by the Mexican forces. Mexican troops were preparing to cross the river. This evidence shows the U.S. was justified in going to war with Mexico because Mexico had killed and injured sixteen Americans,