Do you have American money? If not, why would you bring it to Jamaica.
Just take your Canadian money and change it to Jamaican when you get there at a Cambio which change all the foreign money including dollars both U.S. and Canadian, U.K. pounds, Italian Lire, Marks etc., etc. The Cambios, licensed money changing places, give excellent rates. (except at the airport)
Wait till you get to Negril to do this.
There is no sense in paying for American dollars in Canada to spend in Jamaica when you can change Canadian to Jamaican money after you arrive and get a good exchange rate.
I know; some resorts, restaurants etc do price in U.S. dollars; but they also must price in Jamaican dollars and you will benefit by patronizing places that price in J's.