Hi Ulihake,
I am having the same problem. When I country is once selected for localization by Swiss Knife, the state disappears form the checkout form AND it is required at the same time. I think this is because the parameterfield for a field being hidden itself is also hidden in the localization screen.
Therfore the field State is hidden AND required for the specific country that has been localized thorugh Swiss Knife.
I am using Swiss Knife v 1.9.3. and Woocommerce 2.1.11.
Hopefully you have a solution soon otherwise I will have to dig into SQL tables and remove the record for the localized country, or delete the plugin and all the tables.
Regards,
Dave