Where exactly does this wall go? I'm thinking about the portion of the border defined by the Rio Grande, which is

1. On dry land on the US side? (Eminent domain? How does irrigation of US dry land agriculture work? Or recreational access to a river we own half of?)

2. Right down the moddle of the river? (How?)

3. On the Mexican side? (Not without their permission, and how likely is that.)

The only viable answer is 1., and since most of the land on the Texas/Mexico border is privately held, the condemnation expenses are going to be enormous. And the land condemned mostly belongs to large agricultural owners, who in Texas tend to be wealthy Republicans. They are IIUC mostly opposed to it. And apparently the Wall is going to be as much as a mile away from the river in many places, leaving a big chunk of US residents on the other side of it.