If your item is small enough, USPS Airmail Letter Post is the way to go. I can send one pack of broadheads to Canada this way for less than $3. If it's too big for Airmail Letter Post, your next best option is Airmail Parcel Post, also from USPS.
You will need to make sure you have U.S.A. in your return address, and you'll need to fill out and attach a small customs form to your package.
Be forewarned, although Canada is right next door, some of the slowest international shipping delivery is in Canada. Don't know why but I have consistently experienced that.