This is very strange. I was recently booking with my U.S. card (VISA) a ticket with them, but I needed to choose the ISRAEL location in order to be charged in US Dollars. I guess that you tried to book on czechairlines.com - which location did you choose then?
I agree that it is better to book with the airline, if you want to get the bag included, OR if you want to take advantage of their pre-flight PLUSGRADE offer (upgrading to business, with 2 bags included).