It the UK it depends what field you are in...

Most electronic design engineers don't need to be registered...(I'm not)

Civil engineering/architecture/Electrical you probably do.

Only if it is a restricted health & safety job or needs security clearance. Otherwise your certificates need to be traceable to jump the employment hurdle.

I belong to the IntPE New Zealand Jurisdiction. My handbook gives http://www.abet.org/ as your US IntPE authority. Hope this is useful.

Chemical Engineers in the UK don't need to be, though it significantly improves one's prospects when one becomes Chartered.

If one's skills have been acquired largely organically then Technician Engineer is also a recognised qualification, for which a similar peer assessment route and registration is required.

Recent attempts to protect the Engineering profession in the same way as, say, Chirpody, for example, have so far come to nought. Does the individual who fixes the photocopier class as an Engineer (rhetorical question)?

Ye! A professional engineer puts in more years than a doctor or architech and all you get is classed with motor mechs, and copier fixers etc. an' then you get unqualified project managers, when they've got things wrong and need your help go away saying 'save us from engineers'. Fraid there's only one word for these people ..........

Does it begin with 'a'?

Mechanical engineers in the UK don't need any formal registration or even any formal qualification to practice the art. There are some situations where only a c.eng can sign off certain documents & obviously ones employment prospects are improved by qualification. I'm registered with both the IMechE & IED but, to be honest, I would be hard pressed to show how either of these memberships had helped my career.

The PE licensure system in the US is not national, but rather state controlled and I'm not aware of anywhere on earth such territorialism and exclusivity exists w/r to engineers.

ABET has entered into international agreements about reciprocity of acceptance of International licenses, but the agreements aren't worth the paper they are printed on because ABET has no authority to force the state level organizations to comply. As a result, the US is one of the most agregious violators of reciprocity agreements around.

Depending on where you are needing to have work sealed - you are likely best off minimally supporting local engineers and hiring them to provide any required stamping sealing of documents locally.

You also might find the process of dealing with local engineers elsewhere a real eye opening experience.

No requirement in the Euro countries.

Canada is not overseas for you, maybe overlakes but you need registration if the job requires that (if you need to put your signature as PE). For that you need to contact the provincial association of professional engineers for details and assessment. The process could take years and you might be required to take some exams and even university day-courses. After that you become an engineer in training and for another 2-3 years you have to be supervised by a PE. Some provinces are feeding this way their universities. It is a long political debate on how much this country loses by not recognizing foreign diplomas. The worst case is in health. Foreign MDs and nurses are required first to take an English test even if their first language is English! I know such a case - a nurse born and raised in English Canada, lived for 10 years in the US and came back to Canada. She was asked to take the Toefel test (which by the way is an American English test). It's absurd but everything here is about money, not knowledge.

I think after NAFTA January 1994 agreement then the Canadian Council of Proffessional Engineers (CCPE) has announced the signing of important agreement among the three countries Canada, U.S., and Mexico. that enables the engineers to practice in those juridiction without having to write examination. But Engineers should check with their respective association as ratification of the agreement by each association is required.

As previously stated licensure is a State requirement in US. However, many States practice commity with Canada, except on state special exams. The Board of Engineers does not practice commity with Mexico, in part because they do not have the standardized educational or work requirements typical for US and Canadian licensure. Foreign licensure is highly variable, I know Australia and New Zealand are harsh about their licensure and do not practice commity with US. I also used to had a Geotechnical Principal who was educated, trained and licensed in France. She received commity in California for work and education. Upon state review of her records, she just had to take and pass the Civil exams and the Geotech exams for licensing. A route i would suggest is to use the commity with Canada and get a Canadian license first, then use that for commity elsewhere. By the way US states have recognized the Canadian education, work experience and licensure for some levels of commity at least back into the early 80's that i know of.

Depending on the location you are considering, you need to find the authority that has jurisdiction, make contact with that person or entity, and find out what the particular requirements are. I have PE registration in multiple states in the US, and each state have variations on continuing ed requirements, rules of practice, etc.

Know the rules of the location you want (or need) to work in.