I agree with my colleague.
Law Office of Luis A. Guerra (954) 434-5800. This answer is of a general nature and should not be relied upon as final, nor is it intended as legal advice.
I disagree. Each State has different laws on the validity of such marriages, where a subsequent divorce has taken place.
This will depend upon Canadian marriage laws perhaps in the province or provinces where the divorce and marriage took place. In Illinois, your marriage would have become valid on the date that she divorced her previous husband, but that is only if the divorce was final and legal, but the marriage in question took place in Illinois.
I strongly recommend you contact a Canadian divorce attorney for a legal opinion on this issue. North Carolina may have to honor the marriage, where it was valid in Canada. Perhaps, a North Carolina domestic relations/divorce attorney can confirm this, as well.
This is general information, not legal advice, and does not create an attorney client relationship.
Interesting issue. Even if my colleague Mr. Dixler is correct, for US CIS, it might make more sense to marry again. That might be the more expedient thing to do as opposed to convincing US CIS that the marriage was valid even though at the time it was entered into the prior marriage had not yet been terminated.