A new feature is added to the One Step Checkout - 3 Columns Flat Layout addon:
Smart required ‘State’ field feature: The ‘State’ field is required for all countries with states list or else it will be optional. When there is no default state setup under CS-Cart Settings->Checkout: Default customer location, proper required field style and warning will be shown so it will make sure customers will checkout with State selected
Get the One Step Checkout - 3 Columns Flat Layout here: