What part of their comment assumes that everyone else is from their country? I only see them referring to themselves and their own country.
If I said "we need public transit as a city" am I assuming that everyone lives in my city or am I simply talking about my own city? I don't see why this is any different and it seems very nitpicky.
I think that would be a valid complaint if they had actually lumped everyone in this thread into their statement by assuming that everyone here lives in the US by default, but I sincerely think that any charitable interpretation of their comment reads as "we" simply meaning "the people of my country".