My dear Mr DMcG

You raise some interesting points!

There once was a golden age of course when all musical instruments were citizens of the world and could pass, without let or hindrance, through ports and between countries. Your English concertina, undoubtedly being venerable, was of this privileged generation and could generally pass between states, often by way of a Wheatstone bridge, where such states were separated by a river.

It is also too evident that countries are now demanding identification, often in the way of passports or identity cards, for even more humble musical instruments. Look at the following example of the poor prima domra which now requires a passport even to enter the country of its origin.

Prima domra with a passport

However much your concertina may bellow and get aerated about this, I think it will soon suffer the same fate as more countries clamp down. Whether this use due to the desire to obtain fiscal revenue from what were formerly free reeds or due to environmental concerns (see following picture of illegal concertina dumping in Northern Ireland) is at present unclear.

Illegal concertina dumping

Regarding your son's Japanese-Spanish guitar, this is of course a modern phenomenon and I personally very much welcome this multiculturalism and cross-fertilisation. It is unlikely to be an illegal immigrant. Indeed I found reference to a Japanese-Spanish Mackerel

Scomberomorus niphonius
        
Does your son's guitar therefore look something like this one perhaps?

Yours most humbly,

Dr. Guitar