[Itse]

On getting Mexico to pay for that wall, it's not that impossible.

Private money transfers from US to Mexico are in the ballpark of 20+ billion annually. Since a lot of that money is earned without a work permit, that gives the US government a good excuse to start disturbing those money transfers and maybe even seizing some of that money.

Those money transfers are a huge deal to the economy of Mexico. Make a credible threat to that flow of cash, and the Mexican government very likely gives in.

Or maybe just put a special tax on those transfers.