That should include Mexico and it should be cut off, not substantially reduced.
"... And Mexico is going to pay for it!"
Immediately halt all monetary remittances.
Make an apprehension of any illegal a permanent irrevocable crime, a refusal of entry for life...for any reason. Halt all importation of goods.
Shut down all communications between the US and all offending nations.
Go all Abe Lincoln and Eisenhower on their asses.
Operation wetback, chain deportation.