Cruz renounced his Canadian citizenship.
True, he did renounce; however, it wasn’t necessary as far as satisfying any obligation to the US.
Although they seem to sort of shrug at dual citizenship, the US recognizes only US citizenship as long as we don’t establish residency in another country, by voting or fighting in a foreign army, etc.
Somewhere I remember reading that the US recognizes dual citizenship with Israel (and maybe one other country, not sure).
Well, that’s interesting... I had not known that.