Despite all the problems the US has, I still consider it the best option for the following reasons:

• Higher levels of decentralization and local government control than that of comparable governments. The local sheriff has a lot of authority and discretion in may areas, and it probably wouldn't be hard to come to a "gentleman's agreement" with him that if he doesn't come around asking too many questions you'll police your own and not cause too many problems.
• Large remote areas of low population density which are difficult for non-state actors to mount an attack (eg. regions which are only accessible by boat or aircraft). This isn't unique to the US, but the US being the fourth largest country has more of it than most.
• The nation as a whole is extremely large in relation to the government's ability to police it. If you wanted to disappear you probably could provided you paid your taxes, and the "Rocky Top solution" to dealing with "strangers" could probably work provided it was used very sparingly.
• Its natural resources (eg. freshwater, air) aren't contaminated past the point of being usable
• Despite the present civil unrest, the military is more capable than most of dealing with external threats and isn't dependent on other states for its military

I found a pdf copy of an old edition of this book on strategic relocation online, and I found it useful enough that I'm buying a copy of the most recent edition. It's mostly focused on North America in its scoring, but goes into a lot of detail as to the factors it analyzes to draw its conclusions.