The weakness is still the ocean. Anybody can take a boat from Mexico containing anyone and anything and motor it up to the U.S. The Customs agents agree this is a big problem and no practical solution to it has been proposed.
But a lot fewer would be doing this.
There is a problem: securing the Mexican border will take a lot of money. The only likely way to justify the expense would be to justify it as security against terrorists infiltrating the U.S.
The problem: the terrorists are most likely to enter Canada as refugees, get Canadian citizenship and welfare benefits, and cross the border legally on a Canadian passport...
"The weakness is still the ocean."
Sharks. Sharks w/ lasers strapped to their heads.
No, you're right. I guess we should just `roll-over' then . . .