After attacking Japan today and "lamenting what he views as an unequal military alliance" Wednesday, claiming that if the US is attacked, Japan "doesn't have to help us at all" and "can watch it on the Sony television."

He then lit into Mexico and connected an 1848 Treaty to the crisis at the border.

 Trump also asked why Mexico got paid millions for losing a war against the US in "the Treaty of Guadalupe"... "Mexico attacked us and we responded, then to settle the war they gave us Utah, Colorado and California which were already American anyway, and then they got paid a huge sum of blackmail money." He went on "Who names a Treaty after the woman who used to clean my resort residence in New Jersey?"

The treaty of Guadalupe-Hidalgo called for the U.S. to pay $15 million to Mexico and to pay off the claims of American citizens against Mexico up to US$5 million  Wikipedia

Trump tweeted later and expanded his complaints and connected them to the national emergency at the border, "The Wall will be much shorter and easier to build the further south it is, unfortunately whoever drew the line drew it in the wrong place."

The Treaty was signed under President Polk.

Trump went on to say it was the worst deal ever made and he was "thinking of withdrawing from the Treaty and moving the border straight across Mexico from the southern tip of Texas to the ocean."

"It makes no sense to have a too long border with a river that is drying up, but can still drown people. I'm going over the maps, we'll see what happens." The President added, "They say Polk was a Democrat, I am not surprised."

Leaks from the Department of Justice say Trump wants a question added on the 2020 census for the new American territories reading:

What are the names and dates of birth for household members born before the Treaty of Guadalupe?

A spokesmen for ICE said on White House orders, the Immigration Service has created a list of "millions" of names of Mexican persons who do not match any names from the 1840 US census, or Mexican records from that period.

White House sources say Trump advisor Stephen Miller has convinced Trump people in the new sovereign American territory should be deported if they have any criminal record, to the south of the new border. Those already living there with no criminal record would be given the opportunity to stay in their homes if they can prove they have lived there since 1848.