How to divorce if I'm out of country

In general, if the marriage occurred in Canada, the government in the US will likely legally recognize the Canadian marriage on the basis that the marriage was performed in accordance with the laws of Canada and is therefore a valid marriage in the US. You would need to have jurisdiction to apply for a divorce in the US on the basis of your residence in the state in the US in which you wish to apply for the divorce. You would simply proceed with the divorce application by filing the original marriage certificate in the US state court. Upon being granted the divorce order in the US you would obtain a certificate of divorce, or some similar document, and that would confirm the divorce has been completed and the marriage formally dissolved.