The time required would be measured in, at least, years (Brexit was in most ways less severe, and was a broadly known factor for 5 years before implementation,

The time required would be measured in, at least, years (Brexit was in most ways less severe, and was a broadly known factor for 5 years before implementation, and a precisely known one for over a year before, and there were still very severe problems and many small businesses died), so presumably not attractive to Trump, who seems into instant gratification.