Well, everybody born in the american continent is technically “american” too, including Central and South America. Is there a specific term in english for these people?
Edit: Thanks for all your answers, especially the wholesome ones and those patient enough to explain it thoroughly. Since we (South Americans) and you (North Americans) use different models/conventions of continent boundaries, it makes sense for you to go by “Americans”, while it doesn’t for us.
If somebody called me a seppo, I wouldn’t be offended, I’d just think they were kind of dumb. It’s just too silly to take seriously as an insult.