I'm convinced that the government will not allow a mass invasion or take over or collapse of the government, there is no profit in that. If I had my way, I would design and produce bug out vehicles for those that does believe. The vehicle wouldn't need to get more than 10 miles per a gallon and have a 40 gallon tank. Even the flooding in Louisiana didn't go that far. Why shoot people when you can engage them in slavery. Use your skills to capture them and force them into bondage. Get yourself a whole plantation of slaves and make them do the hard work.
Trump says that the Mexicans are going to build his wall.
How many secret passageways do you suppose they will incorporate into the wall?
That would be like letting the Fox build the Chicken Coop.