Can I implement communication between 2 services situated in different AWS regions using AWS App Mesh? Perhaps, the intention itself is wrong(If so, why?) but I have too little experience in AWS to understand it. Thanks in advance.
AWS App Mesh doesn't help you achieve this, as an App Mesh exists within a VPC, which exists within a Region. You'd have to set up VPC Peering https://docs.aws.amazon.com/vpc/latest/peering/peering-scenarios.html
Or make the called service public, which may or may not be appropriate.