I have displayed filter dropdown for country and language field
I am facing an issue in filtering search with a custom search setting that is set as "AJAX results update when visitors change any filter values"
The behaviour you describe is expected based on the settings for the View.
In the custom search settings, if you choose "Let me choose individual settings manually" then you can specify whether the dropdowns should always show all languages or countries, or whether it should only show possible combinations (so if someone has chosen the US, then only English and Dutch languages would produce results; were someone to choose a different language they would get no results).