What about them? They were in a war and rightly more concerned about the lives of their own soldiers over those who wrongly attacked them, were fanatical in their defenses and were looking to drag the war on as long as possible for as favourable terms as possible in a cease-fire. Had the USA gone down the route of a land invasion it probably would've dragged on for several more months, possibly stretching into years. In the end you would've ended up with a peace treaty with the same war-mongering people in charge as before. Not a recipe for success.