> the tracking is lost as soon as the item crosses the border
That's variable and (often) not the case for shipments to Canada. USPS International First Class would yield a tracking number that has delivery confirmation to the destination.
> Electronic USPS Delivery Confirmation International service — abbreviated E-USPS DELCON INTL — is a tracking service available at no charge for First-Class Package International Service items to select destination countries (see 252.22)
That's variable and (often) not the case for shipments to Canada. USPS International First Class would yield a tracking number that has delivery confirmation to the destination.
https://community.ebay.ca/t5/Buyer-Central/Does-USPS-First-C...
> Electronic USPS Delivery Confirmation International service — abbreviated E-USPS DELCON INTL — is a tracking service available at no charge for First-Class Package International Service items to select destination countries (see 252.22)
Those ~50 countries listed here: https://pe.usps.com/text/imm/immc2_022.htm#ep2686878