A good argument for why secession or other form of breakup is both desirable in many ways and also less negative than at times in the past (Civil War). Does a good job of presenting the pro-breakup arguments (better economic and political freedom, existing cultural splits, and the option for more policy innovation by places like California). Some of these might be strawmen (I assume the author is on the right and doesn't want the kind of innovation California will conduct), but still presented reasonably. The other argument is that some form of breakup won't be violently opposed like the Civil War both because it won't be about something morally odious, and because individual rights, trade, etc. can be protected far better now even in a devolved post-US situation than in the past.

Two things aren't addressed in this argument (and are mentioned in the final chapter of the book, at least the first point). One, the geopolitical risk -- rivalry with China requires the US be at least present size, if not larger, but also of course rivalry with China wouldn't happen if the US were devolved (or if China were devolved somehow...). Two, mass immigration -- it's possible to change the overall demographics of a country through continued immigration, especially with one or two generations of growth after. As a result, any breakup beyond autonomy or increased federalism is probably at odds with the political agendas of both the right and the left, at least of the elites, despite potentially being in the best interest of individuals. ( )