The Postal Service is monitoring a possible strike or work stoppage affecting Canada Post.
Canada Post is the postal operator that performs delivery in Canada of U.S. shipments of First-Class Mail International service, First-Class Package International Service, International Priority Airmail service, International Surface Air Lift service, Priority Mail International service, and Priority Mail Express International service.
If a full strike or work stoppage occurs, USPS will continue to offer customers the option of using Global Express Guaranteed (GXG) service for delivery of documents and merchandise in Canada, with transportation and delivery by FedEx.
GXG service is available online and at thousands of participating retail locations throughout the United States.
Additional information and updates about mail service to Canada are available on the Postal Service’s International Service Alerts page.
source: USPS News Link