Something I remember reading a few years ago, probably during the 2016
election campaign.

If migrants and border-crossers are forced to enter the US through
regular transportation corridors and check-points, the added inspection
required to find these people will horribly gum up the flow of
manufactured goods and hit all sorts of JIT trucking operations.

Hence they want migrants to continue to cross outside the regular corridors.

Now whether or not the democrats are being leaned on / pressured or
influenced more by manufacturerers and trucking companies to NOT build
the wall, for that reason, I don't know, but the Dem's don't talk about
that angle. They are consumed, as we know, by the social-justice angle
of interfering with what they think is the universal human right of
migration.

One thing the dem's did say is that the quantity of drugs flowing into
the US can only come from vehicular transport (ie not individual
migrants) - that is probably true. In which case the solution that
trump should propose is a vastly increased commercial inspection program
at the US - Mexico border. Where the number of inspection lanes and
staffing are increased to find the drugs (and the stow-away migrants)
without impacting legit transport.

Trump should propse this:

a) build the wall
b) inspect every vehicle for migrants (which will increase because of A)
c) because of (b) you will increase facility inspection capability
d) you will intercept more drugs because of (b) and solve that problem
also

That's what the US needs at the border.

But sadly, it also facilitates something that SHOULDN'T HAVE HAPPENED IN
THE FIRST PLACE - which is the US/Canada/Mexico NAFTA/NAFTA-2.

Mexico has shown that it does not deserve the right to free commerce and
access to US/Canada. It does not protect its border with the US and it
does not deserve to siphon manufacturing jobs from US/Canada.

NAFTA is what gave the US it's drug problem. Because NAFTA allowed US
manufacturing to become dependent on an open border with Mexico by
relocating facilities there. Once that was done, goods must flow.
Nothing must get in the way of goods. Car parts, etc. Border security
and inspection must not be allowed to interfere. US politicians must
comply with the dictates of US companies and their lobbyists and their
campaign contributions.