At this time, the states are hardcoded and cannot be modified. You would need to write your custom checkout widget in order to modify the states. There will be a blog post out in a week or two that explains how to do a custom checkout.
This is the code if you wish to add this to a custom widget.
I can submit a feature request
on your behalf to have the states customizable. We are working very hard to implement new functionality.
Please let me know if you have any other questions or concerns.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items