USA follows the rule of reciprocity. If you can legally boat in your own country, then you can boat in the USA. 

In the USA, NASBLA is the agency that oversees all USA resident boating licenses for each state. It is only required for Americans and only required for some states. If you are from a different country, you only must have a boating license from your home country.

There is a big difference between the NASBLA state boating license and a proper Sailing License. The NASBLA state boating license is very weak and only requires basic safety knowledge. There is no on-the-water skills assessment - it is only an online course and test. Whereas the SLC sailing license requires extensive boating knowledge and skills (as well as a legal license (NASBLA for Americans)(home country for others)).

The American National standards for sailing is not a license - it is a training and assessment methodology created, recognized, and promoted by the United States Coast Guard. It is performed on a boat less than 25 ft (7.6m).

The SLC sailing license that NauticEd issues adopted the American National Standards and expanded upon them for larger sailing vessels. It requires the Bareboat Charter Master online courses, an assessment using the bareboat Charter rubrics, a legal boating license from your own home country, and documentation of your experience.

In essence - if you are coming from your home country and intend to go boating in the USA, you are welcome, just have a license from your home country that legally allows you to go boating there. Generally, in the USA, so long as you are seen as boating responsibly, you are unlikely to be stopped and even if the Coast Guard stops you, they have no jurisdiction over state boater licenses, They will check your passports, check you for sobriety, and perhaps a drug check on your boat and send you on your merry way with a friendly wave.