here in the USA there is no such mental or physical health disorder/disease called imposter syndrome....

that said human beings are taught as very young children to play pretend,use their imaginations to pretend to be other people and characters. this kind of thing permeates our lives from what we read, watch on tv, go to a theater and you will find many people acting out the parts of other people and characters. theres even "fandoms' where some people emulate their favorite actors and themes as a way of life. examples the star trek trekies, elvis impersonators, and other impersonators of favorite popular persons. even on line we are told not to use our real names to make up someone and many people use identities on line that portray other people/characters/animals and such...

that said there are crimes related to people who steal anothers identity but its not called imposter syndrome. its called identity theft.

I dont know about other countries but here in america there is not yet such a diagnosis of imposter syndrome in the DSM 5.