There are different levels of maturity of airline operations and plane reliability between countries, and this is recognized by both the EU and the US. They bot

There are different levels of maturity of airline operations and plane reliability between countries, and this is recognized by both the EU and the US. They both have different lists of airlines (for the EU) and countries (for the US) that are not allowed to operate in their respective airspaces without a wet lease (a lease from another company where that company assumes maintenance operations and provides the personnel to operate the plane). It also doesn't really make sense to put regional carriers from small countries (eg. Gabon or Kyrgyzstan) in the same bucket as strictly regulated large carriers that follow the ICAO standards.