6/ It is very normal that different communities refer to the same place by different names.
München in Germany is called Munich in English.
OpenStreetMap handles this by using different tags, "name:de" versus "name:en". Tags can specify alternative names, official names, etc.
So one likely possibility is that the name:en tag remains "Gulf of Mexico" while official_name:en-US is set as "Gulf of America" (and of course name:es remaining "Golfo de México")