Depends on the item... for anything going by box... expedited and tracked airmail to the USA is usually cheaper than regular untracked surface once you factor in venture one/small biz rate discounts, not to mention way faster. Hell even in canada its cheaper to ship expedited than regular mail once you get the discounts (they don't offer discounts on the most basic service level).
On those Small Packet weighbills printed using PayPal and going AIR to the USA or Overseas, with bar codes and numbers that ARE NOT trackable, I always ask my Postal Outlet counter staff for a receipt. It is readily available at no charge and is proof that the parcel shown as shipped in eBay, was in fact turned over physically to Canada Post with some of the pertinent info. It helps when dealing with "crooks" who insinuate that you may not have actually mailed his/her parcel? Yes a Seller's feedback may be Great but there are people out there who would dearly love to give him or her a Black mark. PayPal defends the Buyers and Sellers can't give them Negatives?? That's and old one; let's not go there.
In 2014 which was when the previous posts were made I don't think that small packet had a bar code that could be scanned. I sometimes do get a scan for those packages as well although that would not help in an inr case as you need proof of delivery. They can be used for some insurance claims as proof of shipment and In some cases, PayPal may accept them as proof of shipment in a cc unauthorized use chargeback.