All registered mails and packages are hand delivered by the destination Post Office. That is to say, mails to USA will be delivered by USPS; mails to United Kingdom by Royal Mail, Mails to France by France La Poste e.t.c
Postal delay can happen for a number of reasons in foreign countries. E.g. bad weather condition, political climate, custom issues, duties and taxes, destination internal mail route delay e.t.c. Unfortunately, all these factors are beyond the influence and control of third party.
If the package remains undelivered after a reasonable transit time (at least 18-working days), the recipient / addressee may also check the delivery status with their destination post by providing details such as the registered number to their Postal Administration.
Contacting information for some of the popular postal network as follows:-