Am I the only one that doesn't see a whole lot of difference between someone being planted in his campaign and someone already in his campaign reporting to the FBI?? I mean, it feels like we're arguing technicalities here... They had someone inside his campaign. When or how they got there doesn't make THAT big of a difference.
Well technically Canada was part of the British Empire then and they are still part of the commonwealth today, they even have Queen Elizabeth on the loony. Trump just probably got confused, that's all.
In all seriousness though, if it was said, I can more see it being said as a joke than as a serious retort. Sounds like something he would do and think he was being clever.