OK, here is a sample sea service letter:
TO: USCG office (wherever)
This is to certify that Mr SailorOlive SSN 123456789 has served in the capacity XXXXXXXXXX aboard the following vessel: F/V barrier reefer, Official no, 123456 25 Gross Tons, upon the waters of Sydney Harbor upon (oceans, nearcoastal, inland) waters. Mr Sailorolive worked from jan 01 2001 to jan 31 2006 for a total of 365 days underway.
Mr Sailorolive stood 8 hour navigation watches as master of the vessel.
Signed, vessel owner, or supervisor.
If YOU were the owner you can sign your own letter. You will need a separate letter for each vessel (unless they were owned by the same company)
With these letters you will be able to satisfy the sea service requirements to be approved to take the USCG exams when you get here. Unfortunately your courses and exams you took there aren’t worth anything here (except as a prep for the USCG exams) The USCG typically will give 1.5 times the tonnage to ‘step up’ to a bigger license. So if you have a predominant amount of time on 25 ton vessels you will get a 50 ton license. If you have time on a 50 ton vessel you will get a 100 ton. I know its not 1.5 times, but they work in 50 ton increments. Depending on which license you are looking for, there may be other courses you may have to take, CPR, First Aid, Radar Observer, Firefighting, Water safety, Social Responsibility, vessel security officer, Celestial Nav course (if you want oceans) and more, if the CG has a hair across their ass about your experience!
You do know there are ‘license mills’ here in the US that specifically teach you the exam. In your case this is probably exactly what you need, since you have years experience, you just need the US exams. One of the schools is “SEA SCHOOL” google them up.