How can EMC standards be globalised when the power sources differ in frequency and amplitude across the globe? Won’t the specific criteria for each country differ for domestic items?

Well this is the stock text from the IEC website - The Scheme is essentially based on the use of international (IEC) Standards. If some members national standards are not yet completely harmonized with IEC Standards, national differences, Special National Conditions (SNC) and Regulatory Requirements are permitted subject to formally declaring and detailing them to the IECEE Secretariat for further publication. The CB Scheme utilizes CB Test Certificates to attest that product samples have successfully passed the test conditions and are in compliance with the requirements of the relevant IEC Standard(s). When applicable, the CB Test Certificate and its associated Test Report can also include declared national differences, Special National Conditions (SNC) and Regulatory Requirements of various member countries. The main objective of the Scheme, is to facilitate trade by promoting harmonization of the national standards with international Standards and cooperation among accepted NCBs worldwide in order to bring product manufacturers a step closer to the ideal concept of "one product, one test, one mark, where applicable'.

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