Anyway, a common denominator here is the sufix -land. The Netherlands is an exception (the word Netherlandish does exist but is hardly ever used and does not sound right anymore).
I guess Switzerland and Thailand didn't make it because, you would get Swissish/Switzish (which it might have been at one point, you can see how that easily turns into "Swiss") And Thaiish
As for the others on this list, I am sure the speakers of þe Olde Ænglisc had a good reason ;)
The quiz idea is really great though, I enjoyed the quiz a lot!
That's why I wonder why British has got the second lowest rate after Luxembourg, though UK looks the most influential one among these ish countries...
I've met Scottish people who would punch you for calling them anything other than Scottish!
Get over yourselves.
On my hand I have a dish.
I have this dish to help me wish.
When I wish to make a wish,
I wave my hand with a big swish swish.
Then I say, "I wish for fish!"
And I get fish right on my dish.
If you wish to make a wish,
you may swish for fish with my Ish wish dish.