Thank you. That explains it. It makes a difference if he's a naturalized citizen versus a born citizen.
One thing for all of you to keep in mind as you progress; I am a dual citizen because I was born, in Canada, to a Canadian father and American mother. Canada considers me a citizen because I was born there; the US considers me a citizen born abroad to an American citizen. However, even in my case, which is not the same as your husband's, the Canadian consulate said to me, "Canada recognizes the concept of dual citizenship. The US reluctantly acknowledges that other countries recognize the concept of dual citizenship". As you go forward, understand that it is difficult to obtain citizenship in the US without relinquishing your other citizenship. It's not impossible, but it's difficult.