Why privatize? Where is the demonstrated need & benefit?
The Canadian system is a not-for-profit private system that by all visible measures appears to be working well, and may be worth examining as one example of a "privatized" system.
But I don't think this is what Mr Trump has in mind; I think the vision, such as it may be, is more like, for example, private, for-profit prisons and I don't think there is a working example of such and ATC system, at least of sufficient size, to show that for-profit ATC works the same and as safely as the generally-accepted way.
Profit-making and profit targets have a way of altering priorities and while SMS for example may now be reasonably cited as an example of successful, internal self-auditing that maintains safety, I dont' think the same outcomes could be ultimately expected in a private, for-profit ATC system.