What you stated as the good old days was never true. Citizenship status was dealt with in the first Congress, by the same men who wrote and ratified the Constitution. There are two types of citizens, natural and naturalized. Natural as defined by the same men who wrote the Constitution is citizen from birth. What you describe has never been the case in the United States from 1789 till present.
Prior to 1965ish it was illegal for a US Citizen to have dual citizenship. So young Ted would have to choose US or Canadian. Anyone that has legitimate dual citizenship is not (IMHO) a natural born citizen. Someone pointed out that Germany considered a child born to American parents on American bases as German that is not (again IMHO) legitimate and such a person should not have to take any action to affirm there NBC status.