Some banks have international partners that have lower fees. Just as an example, here's the way it works with Bank of America. We've used BNP Paribas in Martinique and got a better rate. I assume it would work the same way at a branch in St. Martin.

https://locators.bankofamerica.com/international.html

For our last trip to St. Martin in December, we just used USD and a credit card and never actually withdrew from an ATM. This was the first time we didn't use local currency, but it worked OK near Orient.