The support staff I spoke to said she was unable to change the country, and I persuaded her to speak to her foreman who also said that the address' country was unchangeable and that they are maintaining to their public policy in these kinds of situations. Your mileage may vary.
If there is going to be any problem with this, Im going to resend it same day. The package goes from CN to CZ only 2 working days so thats not such a big difference.
I made some address changes few weeks and months ago - CZ-FR, CZ-IND, NOR-CZ and some other. Weird you have a problem with that now.