This offers literally none of the security properties that are required for a secure decentralized currency and betrays a very fundamental misunderstanding of what proof of work is for or its (economic) security properties.
The most obvious problem with this proposal is that it’s clearly not secure - if someone manages to make fake passports (either because the cryptosystem isn’t secure, they steal the signing key, or they control the passport issuance authority) they fully control the system.
I answered a solution to this in another comment, above. If the mining difficulty is set by country, it would take 51% of the countries to go rogue in order to perform a 51% attack.
So what you're actually proposing is a blockchain where the mining process is based on e.g. UN member countries voting. Cool, but that's not proof of work, it's not a cryptocurrency, and it's not very useful. They already have something a lot like this - it's called "Banks in the EEA".
The most obvious problem with this proposal is that it’s clearly not secure - if someone manages to make fake passports (either because the cryptosystem isn’t secure, they steal the signing key, or they control the passport issuance authority) they fully control the system.