The ironic part is, we became the wall. Many immigrants stayed in Mexico because they couldn't cross to USA. Trump invited our wimpy president to a secret meeting, afterwards Mexico silently made the change of attitude from country of passage to destination.
Yeah: If someone donates money to the government for any purpose, that becomes government funds, and the Constitution says Congress and only Congress has the authority to decide where those go. Not the President.
So either Trump is doing this officially as a President, but with funding that is illegal/unconstitutional...
... Or the funding is legal, but Trump is doing it as a private citizen, which is a federal crime. [0]
The Supreme Court will jiggle the constitution and some forgotten legal precedent from the magna carta will fall out and 5-4 this is actually not a problem at all if you think about it.
Doesn't matter if a trillion dollars was shat by God himself out of a plane into the Treasury. They failed to get historic district planning permission, they failed to save historic materials and objects, and lied about the plan. The now revealed plan is an gaudy, boorish, tasteless, and tacky abomination because that is the essence Trump.
Conflict of interest by attempting to curry favor for his vanity project by making donations? That's a fair criticism.