Not enough lift capabilities worldwide to get the manpower into the U.S. to do a proper invasion.
Sure there are enough tanks and firepower just not enough ways to get them here in a timely manner.
Hell the run up to the invasion of Iraq took months of logistics. And at that you had the U.S. military, the only outfit with such abilities.
And Iraq is what, the size of South Carolina?
All great points.
Amatures talk about tactics, professionals talk about logistics.