positive results of the Manifest Destiny was that America gained alot of land. They fought a war with Mexico during the 1800's called the Mexican War.It was a land dispute ov … er Texas. The majority had voted to join America, but Mexico still wouldn't let them.he negative result is more then half of the native population was destroyed. to the point it was genocide. the race of the native american people decreased. Loss a lifes and the stealing of land should without a doubt be a serious set-back for moral-high people.