When foreign ambassadors live for years in the U.S., there must be babies born here. Are those babies American citizens? I’m not sure how it works, but I assume the babies are citizens of their parents’ countries.
If any foreign baby’s parents aren’t American citizens, then neither are the babies. That’s what makes sense to me.
Childern of foreign diplomats born in the US are not US citizens. This is not allowed by law. They same law could include foreign nations as a whole, illegally and/or legally in the US at the time of birth. This is what is meant by the jurisdiction clause of the 14th amendment. What cannot happen is to retroactively remove citizenship. This would be an ex post facto law, which is not constitutional.