Coastal or Bluewater...
I think the bigger issue is satisfying the authorities you''ll encounter along the way and then when you get home. Don''t sail the boat in US waters without proper documentation papers / registration. This has nothing to do with being or not being a US citizen. Proper ships papers are an international requirement everywhere in the world. Not having them could land you in jail and your vessel confiscated.
I would work this problem backwards and start with where your home port is to be.
If you are to make the boat a US documented vessel and it already is one (many in the size you might buy can be) then it''s a simple transfer fee and paperwork. You''ll then have US papers good any place you might go. Your country will have it''s own rules.