You could always make an appointment with one of the US consulates in Canada, they are typically in the major cities, Vancouver, Calgary, Winnipeg, Toronto, etc, or send the CBP a email asking. I searched online to see if one could check their Visa validity online, nothing came up.
One question, did you come into Canada thru the US border? In a nutshell, you got a US visa, arrived into the US, and then came to Canada and claimed asylum? If you did that, it is looked upon as abuse of the visa approval system, as well as mentioned above, the IRCC shares data with the US CBP, and more than likely your visa was cancelled once you claimed asylum
Note that you may be refused entry (even with a valid B visa) since you are now married to an American and should be pursuing a K-3 to move to the U.S.