You can disable the state drop-down in the checkout form in the Web Store and Inquiry Catalog modes. Go to Products > Settings > General Settings > Shopping Cart (Quote Cart in the Inquiry Catalog mode) and find the Form Settings section:
Once you check the Disable State Field checkbox and save the settings, the state field is removed from the checkout form.
With Shopping Cart PRO or Quote Cart PRO, you can fully customize the checkout form with checkout drag and drop editor. You can also set conditional fields and paid options for the customer.