Where in America?
I''d rephrase your question somewhat: "From where should we depart given our plans to circumnavigate, given that we''ll be working hard on the boat and will probably sail long distances not at all before our departure, and given that our initial cruising grounds will - in truth - be a shakedown period for the boat''s gear and crew before doing a circle?"
If you plan the circle that most crews choose, the bulk of it in the tropics, you''ll want an initial shakedown period in which boat gear/systems you''ll need to depend on in the tropics can be trialed and adjusted (awnings, bimini & dodger, ventilation, good/efficient refrigeration if you plan on having that aboard, water maker ditto, good deck collection system when it rains, etc.). Departing San Diego will get you cruising in Baja and along the Mexican coast, with a season to sharpen up your skills and not too far away from the U.S. infrastructure for the things you need. Jumping off from anywhere in the Southeast will do the same thing re: the Caribbean...but the U.S. infrastructure is a bit more accessible from Puerto Rico, USVI or Trinidad than it is from Mexico, at least when you look at importation issues, chandlers on hand, and such. RE: your shakedown period, a Caribbean run can combine numerous offshore jumps, short or long depending on how you feel and with weather not much of an issue, while visiting a variety of interesting cruising grounds. (We found Trinidad, Puerto Rico, the DR, Haiti, Jamaica and Guatemala a fascinating mix of cultures, histories, and sights to see - and most of those could be folded into a sea trial period when leaving from Florida.
I see no reason to prep and work on the boat in such a tough climate as the Great Lakes or the Northeast. The Northwest is barely better, and the Gulf is only a marginal improvement when compared with SoCal and Florida (either coast).
I''d recommend starting with those guidelines and then see where the boat is, after which you can sort out how ''she'' and your crew can end up in one of these areas in the easiest, most satisfying way possible.