Well, sorta?
The name was changed for US users, as google's policy is to use whatever a user's country's official name for something is (also true for where borders are drawn and so on). In mexico (and presumably every other country), it's still "Golfo de México". I don't know if they'll change Lake Ontario to whatever it was trump did but it would surprise me if they didn't, and just as with the Gulf it's going to only be americans that are impacted & everyone else will be continuing to ignore his nonsense.
edit: (You apparently can change your domain to view what it looks like from other countries - though I couldn't figure out how to do it in the ten seconds I tried just now. Some domains display some alternative names in parens too I'm told, though I haven't looked into that one at all. I know in Mexico and Egypt it didn't show up as Gulf of America when I checked, so there's that. The next most famous example is the shitshow that is the Persian Gulf / Gulf of Iran / Arabian Gulf debate.)