>The shortage of HT drivers seems to be an international phenomenon. NZ has a highly effective moat to prevent illegal migration, so the market will be forced to do its duty and authorize skilled migrant categories or incentivise training or raise wages until demand is met.

>>If the US had a moat or wall, the market would be forced to do the same rather than encouraging illegal immigration that depresses wages and consumes jobs that citizens might like.

One of the many myths that pervade US politics.
We use immigrants to cut lawns and wash dishes because no native citizens will do that work.
I was able to put myself through college by caddying at a golf course and eventually becoming caddy master.
Golf carts have replaced caddies largely because high school and college kids no longer wanted to do that work.

There's something else at work here.

https://www.nytimes.com/2018/06/15/business/men-unemployment-jobs.html

There are more than 10 million men between 25 and 54 in the US who just dropped out of the work force.

No wall involved there.