Unfortunately many countries are like the UK. Last time I checked US, Australia and New Zealand would require you to undergo training and examination to get their licence, albeit sometimes a shortened course. Plus, you would have to satisfy immigration/residency requirements first. It might be one thing having a recognised licence but it is worthless if you can't get in to the country.
I would also be wary about who is offering the job. How many places does Serco operate at in Canada? Don't NavCanada do most of the ATC? Same in the States. FAA do most whereas the private operators just do level 1 towers, although I believe that might have been changing to allow slightly higher rated towers.
I may be wrong but I get the impression that national authorities that recognise overseas, or even ICAO, licences, are places that most would be wary of living in, or it is for posts at units where the locals don't want to work! There will of course be some exceptions but most would give priority to their own folk.
The UK isn't alone!