Seeing that Trump has won the election, the big question is now: Will he be able to build his "great wall"? And will the mexicans pay for it?
Okay, that is most probably the least of the problems the US and the world has should he turn out to be as loony as his critics make him look like, but still... it was one of his most "out there" promises made during the campaign, and given part of his demographics might actually have BELIEVED him even in that case, it is a promise that he might feel obliged to keep.
Now, given that the US probably does not have the money for funding such a project, and anyway the US taxpayer does not want to pay for it, Trump would want to have the mexicans pay for it (as Trump has promised during the campaign).
Ignoring the fact that if the US couldn't pay the cost, Mexico couldn't anyway, is Trump stupid enough to risk a diplomatic crisis when telling the mexican government the good news?
Given that the rest of south america isn't really that fond of the Gringos (neither are the mexicans... had to tell everyone that I am european before they would start talking english with me), and probably would figure out quickly that if the new President of the Gringos is crazy enough to ask such outrageous things from the mexicans, they would soon have US special forces all over their countries again hunting real and imaginary criminals without asking for permission first, this worsen the relationship to many or all south american countries...
Or will he just not mention it, like, ever again? Because it was just a lie made to gain some publicity and votes? And if somebody asks, stall and defer hoping they will forget it again?
What do you think he is? A liar, or a foreign affair trainwreck?
Really, I am not a fan of his, I think most promises made will ultimately not be achievable, but most of them are not so explicitely looking for trouble with a direct neighbour.
My personal opinion: You most probably will not hear of this borderwall against mexico from Trump, like, ever again. IF he is as much business man as he would like everyone to believe he is, he will know this is a stupid idea best left on the drawing board.
Maybe he WILL do something against illegal immigration from mexico... but IF he builds a wall, it would be on US taxpayers money. Which he probably does not want to do.