The default country and default language for an Integration should be set to your website's defaults. If you're a based in the US, but sell internationally, you should set your default country to United States and your default language to English.
You can set your default country and default language from the Advanced Settings tab in settings for your Integration.
How does this affect the control?
If the user is located in a country that you have deselected in your Integration then we will show them the manual address form with your default country chosen from the country dropdown. For extended scenarios, see documentation here.
If your customer's language is not supported for the country in which they are located (e.g. German in USA) then we display labels in the default language.