To clear few things up: GOG offices are based in Warsaw, Poland (as it's a home of our parent company CD Projekt), the GOG.COM company itself is registered in Cyprus (for business reasons), and this is where the transactions are registered. Our web servers are hosted in Canada, and our download servers are all around the world for optimum transfer speeds.
If you have problems with using your CC on gog.com you should contact your bank to clear things up. You should also be able to use PayPal without any problems.