Salesforce module provides you with the ability to select "State and Country Picklists" option. It changes the country and state fields in Salesforce to leverage "drop down" form fields
IMPORTANT: If your Salesforce org is configured to use/not use these picklists, you will also need to activate/disable their usage in Magento via Salesforce configuration
Case1. "State and Country Picklists" option is set to "Disable"
Go to Magento Admin panel - click Salesforce (on left side bar) - General Configuration - Advanced tab
2. Set "State and Country Picklists" option to "Disable" and Save Config