Lots of qualifications are unacceptable in other countries without passing the local exams. Before you allow someone to do certain things you want to be sure their qualification is appropriate so you need a mechanism for it. The EU provided that mechanism.
Each State/Territory/District in US and each Province/Territory in Canada is probably (in Maryland and Ontario definitely) requiring local licenses (for a fee, after local exams) for electricians, plumbers, realtors, schoolteachers,.. , and (of course) motor vehicle drivers*. An electrician we used in Ottawa (Ontario resident, anglophone) complained to me that he lost business to rivals who lived across the river in Hull (Quebec), who had taken and passed the Ontario qualification (set in English). For him to get the Quebec qualification he would have to take the Quebec tests in French, which he could not speak well.
Both US and Canada do, of course, have nationwide, Federally-administered, aeronautical
licences (tests available in either language in Canada, of course) for pilots, ATCOs, engineers etc; but neither nation instantly and without further tests recognises those of the other.
[*every 2 years after Congressional elections, Maryland media enjoyed publishing pictures of distinguished in home State but new-to-Congress politicians and their family members taking a number and waiting in (long) public line at the Motor Vehicle Administration to take their Driver Permit exams and getting Maryland 'tags' for their vehicles. This had to be done within 3 months of become resident in the State. And they had to pay State Sales Tax (assessed at State-administered 'book value') on the vehicles they had brought with them from their home State.]
(mere guide at) Jet Age Museum, Gloucestershire Airporthttp://www.jetagemuseum.org/
TripAdvisor Excellence Award 2015http://www.tripadvisor.co.uk/Attraction ... gland.html