State custom field should't be required. There are a lot of countries not using the notion of states.
Go to Settings > Custom Field and click the edit option of field and set it not required. Check image for reference This will solve your issue.
Sorry!! This is not what I meant. apologize! Let me reword this. States shouldn't display for countries that have no such things as states. Right now, if you create an ad and chose a country such as Germany, France or Switzerland for instance where states do not exist, the state field will still display even though it's not required. So I added the notion of "none" or "n/a" in the selectable list but it would be much better if the states field would display only when needed. Thx.