"Closing the border" isn't a realistic option. We are a country that does business. We can't do business if our doors are locked shut.
The US-Mexico border spans several states... so unless we station an armed guard every 50 feet along the border and stop (and thoroughly check) every
vehicle (car, truck, or train) crossing the border, then there will always be meth (and whatever else you can imagine) coming into the US.