I’m would be interested in hearing about recent experiences entering the USA, in particular from anyone applying for a VISA at the CBP port of entry … we are planning to transit into the USA from Canada following a North Atlantic crossing this summer, then intention then being to sail south along the eastern seaboard towards South America.  My recent enquiry to the US immigration tells me we need B1/2 visas, and that there is a long wait to get an interview for these, but also advises I can contact the CBP to enquire about local procedures nearer the time, it also tells me that I would be granted a 1 year licence.. so I imagine I’ve we return to north America 
following our time in the south, that we will have to repeat the process if it’s outside the 1 year licence