It’s probably worth having; Johnson is always interesting, and when he’s unreliable you can tell right away. His book Modern Times is an excellent (world) history of the 20th century.
There really isn’t a libertarian history of the U.S., I’m sorry to report. I’ve done a bit with my Politically Incorrect Guide to American History and 33 Questions About American History You’re Not Supposed to Ask. There’s Schweikart and Adams’ A Patriot’s History of the United States, but it’s much worse than the Johnson volume. This is a project for someone to do.
There are decent treatments of particular episodes, time periods, and historical figures, but no overall text.