My point is that Rubio’s parents were foreign nationals, not US citizens, at the time of his birth. Whether they were in the country legally or not is a non-issue. They owed allegiance to Cuba. If little Marco was born before they had time to become US Citizens, that’s just too bad.
There are a great many of us that can't trace our heritage on both sides to the Mayflower. If you can great. People born in the US to legal immigrants whether they have become citizens or not are unquestionably citizens. Knowing the law is important. "If(paraphrasing a Mark Twain quote) you don't know the law It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt."