In light of recent events, here's OpenStreetMap editors discussing naming of the Gulf of Mexico
(community.openstreetmap.org)
So now that is in the hands of the folks who use the OSM data. It's in a somewhat exotic tag, so by default any map that uses OSM will still show Gulf of Mexico, unless they actively intervene to show Gulf of America. So if you see an OSM based map showing the latter, you know they made that choice consciously.