and then start the Great Wall Project on BOTH borders. Jobs and economy boosting for everyone along with permanent American security to boot.

You'll need those wall building jobs to employ all the people thrown out of work by choking off trade with Canada, and you won't get a whole lot of security out of it. The terrorists can fly in legally from Saudi Arabia pretty easily.

(Besides, the US is so far in debt that there is no way the government could afford to build a wall several thousand miles long.)