The wires that are part of the machine itself are not and NEC issue. Think of the machine as an "appliance." The NEC pretty much stops at the connection.
Sure, SOME appliances need to be 'listed,' and standards exist for them ... but even in those cases it all comes down to 'engineering,' rather than codes.
So, what does the American consumer of foreign machinery need to specify? Well, we need approariate attachment points and the ability to bond the machine to our grounding system. We need proper identification and labeling- after all, those 'receptacles' on the machine might look 'normal,' but I bet they don't supply 120v 60hz!
It also comes down to 'trust.' And, at the risk of being politically incorrect, you need to have some understanding of with whom you are dealing. While some cultures (Japan, Germany, Switzerland, etc.) are quite technically competent and make a virtue of fine engineering, others (China, Nigeria, Albania) have a very different set of priorities.