Don''''t know much
The last time I checked, the USA had not yet annexed every country on the planet. So at the very least, expect to be asked for your passport whenever you travel abroad.
With regard to what else you''ll need, contact the US State Department, the Embassy of China, and the embassy of any other country you think you''ll want to visit.
As far as the size and type of boat, the answer will depend on your: sailing ability, financial resources, living requirements, and your luck or lack thereof. ;^)
~ Happy sails to you ~ _/) ~