Aquí os dejo las características del servicio que aparecen en la propia web de US Postal en donde podeis comprobar que efectivamente el servicio de certificado(es decir con número de seguimiento)es un extra y no se suministra salvo pagando una tarifa extra:
First-Class Mail International
Ship virtually anywhere at reasonable prices
The most economical way to send letters, large envelopes, small packages, postal cards, printed matter, and small packets 4 pounds and under, worldwide.
Outstanding Value - Postage starts as low as 75¢ for a one-ounce letter or postcard to Canada. This service lets you communicate through the mail with letters to customers, businesses, and loved ones across the world.
Extra Services - Registered Mail service without insurance is available for a fee.
Resource Center
Print customs forms online, check out Extra Services like insurance and Registered Mail™, and follow mailing conditions with Service Updates.
Additional information about First-Class Mail® International is available in the online International Mail Manual
También podeis verlo directamente en el link
http://www.usps.com/international/airmailinternational.htmEn cambio Priority si que da ese servicio de seguimiento como podeis comprobar:
Priority Mail International
Priority Mail International offers reliable service at economical rates.
Priority Mail International (PMI) provides customers with a reliable and economical means of sending correspondence and merchandise up to 70 pounds
to over 190 countries and territories worldwide.
Priority Mail International offers:
Flat Rate Shipping Options - Flat Rate envelopes and boxes available for PMI shipments. View flat rate prices and order supplies.
Outstanding Value - PMI is priced lower than our competition's published rates for international shipping.
Online Discounts - Receive 5 percent off any PMI shipping label printed and paid online.
Online Tracking - Put our delivery information to work for you. Track PMI package shipments. Note: Tracking is not available for Priority Mail International Flat Rate Envelopes or Priority Mail International Small Flat Rate Boxes.
Convenience - PMI shipments can be handed to your carrier, dropped off or brought to your local post office. Free carrier pickup is available for this service.
Por otra parte el servicio de Correos en USA es un poco mas complicado que en España por algunas particularidades especiales que abaratan el propio envío dependiendo de circunstancias que si alguien tiene interés y dada su complejidad puedo explicar por privado ya que no aparecen en la web de US Postal y que en general mucha gente desconoce y de ahí que el mismo envío pueda tener una variacion de precio en ocasiones escandalosamente alta.
Es por esto que a la hora de afirmar o aplaudir ciertas afirmaciones yo recomiendo siempre cautela porque estamos acostumbrados al sistema español de peso,tamaño y tarifa y en US Postal entran en juego factores ajenos a la propia US Postal.
