Have you driven near the border? Driving through west Texas I was met by stop and go traffic for 5 miles. Middle of the desert. I kept driving and realized border patrol had blocked the interstate and was diverting traffic through a checkpoint. Hundreds of cameras and drug dogs everywhere. I drove up and the agent asked me if I'm a US citizen. Then I was free to go.
It's not that simple. It's very very hard to travel if the government doesn't want you to.