While the ABPath absolutely refuse to make exceptions for US residency training requirements, it IS possible to get specialist recognition outside the US as a AMG. However, it is a fairly difficult road to travel, and in many instances the decision not only varies from country to country, but from case to case. I personally know of examples where people were required to redo ALL of their pathology training in Europe, even though they had passed US boards.
In fact, there's not even a uniform standard for getting a plain license, except in the UK which has the PLAB.
It's somewhat odd, because I find it really difficult to point to specific differences between training in Europe and the US, but it probably comes down to tradition and politics. If you look outside Europe, the picture is even more blurred. For instance, UK qualifications are basically instantly recognized in Singapore, and partly in Canada and Australia, but those same countries can be very sceptical if your qualifications were optained in say Germany or France.
If somebody really wants you, there's always ways around the bureaucratic red tape, in any country. But if you just want a change of scenery or are moving for personal reasons, it CAN become a major headache.
And on top of everything else, visa and work permit rules are constantly tightened all over the world. It's probably fair to say, that the US today is significantly easier to work in as a foreigner, than it is to go to Europe as an American.