I am an Australian citizen who has done half of the Great Loop.
I know it is hard to believe, but you do not need a boat operators licence in the US (unless you have paying passengers/cargo). You can buy a big, powerful boat and do the loop with no formal training requirements.
But do get an insurance
policy brokered by Boat US and get their Gold Unlimited towing plan. It is the gold standard, and a bargain because most US boats are hardly used. If you bump another boat it could be very expensive without insurance
You do need to comply with state and federal safety
requirements. Go to the the USCG web site and study the safety
requirements because you are going to be stopped by them.
Do not register your boat in New Zealand
or fly a NZ flag (unless federal rego is necessary for Mexico). If you do so it creates a buraeucratic nightmare within the US. You will become extremely frustrated. Better to have state registration
and fly a US flag. I sailed in the US and Canada with state rego no problem. When I got Australian registration (on the way out) it made things very difficult. The Austalian flag attracted problems.
State to state differences are minor - different limits on alcohol for example. Extremely lax compared to Australia
. The Great Lakes
and many other waterways are a no discharge zones. You need a good way to manage your waste.
Law enforcement is going to assume you are in the country legally and you will get a warm and curious reception
from all segments of society. The Cities are very safe, even Detroit. If you do not buy and sell drugs then no worries.
Get a US address via St Brendans Isle. It will make everything easier.
Will be a fabulous trip, good choice. And don't miss the Exumas
in the Bahamas
, for goodness sake. That is a highlight.