If a country were to send their military to invade our country then all Americans would unite to repell them, would they not? So the best way to invade America is for the military to not were uniforms or carry weapons. Just walk accross the border over time and take up positions around the country and when enough arrive arm themselves from the abundance of weapons in this country and then choose a time to strike. We have allowed Mexico to successfully invade America and now we are just waiting for the hammer to fall.