Actually, no, I never vowed citizenship to the United States. They gave it to me; otherwise I would have been stateless. It was the United States that came to my rescue.
As far as applying is concerned, I know about that very well, because I had to apply to become a landed immigrant in the country I was born in. I was a Canadian citizen. I know the ropes. But Canada has signed a convention against statelessness. I've had several talks with legal departments on this.