How to unpublish an android app only from a single country?

If you are using Google Play Console Beta, Navigate to your app > launch > production. Then move to Countries/Regions tab. Now click on Remove countries/ regions to get pop having list of all available countries.

You only need to do the next

Select the country to disable or enable

Link about the steps

https://support.google.com/googleplay/android-developer/answer/7550024?hl=en

Steps

To manage your app's availability:

Go to your Play Console. Select an app. Select Store presence > Pricing & distribution. In the "Countries" section, select Manage countries. Update your app's country selection. If you add a country for a paid app, new prices are automatically added. If needed, you can then edit local prices. Submit your app update. Note: For details on how to target a staged rollout to specific countries, go to release app updates with staged rollouts.

go to production and select countries/region remove or add

In the google play console, go to Store presence -> pricing & distribution. Click on manage countries and you can make your app unavailable in the desired country and submit an update.

Try this:
1. Go to your Play Console.
2. Select your application.
3. Select "Presence in Google Play Store" > "Price and distribution".
4. In the section "Countries", select "manage countries" and in these section select only the country you want.

Names of sections may be different because I have the console in Spanish.

I hope it helps you, regards