Remove all countries at once except one.

How does one remove all countries except one without having to go through hundreds of clicks one by one?

Please don't just say edit SQL without more info about that.

If you're 100% sure you want to remove them, an SQL command would be enough. You would need to know the ID of the country, but you could go with the name... For example, US is 223, but you could use "United States" as well.
admin->Tools->Install SQL Patches

DELETE FROM countries WHERE countries_id != 223;

or, based on name:

DELETE FROM countries WHERE countries_name NOT LIKE 'United States';

As always, don't just run the query, make sure you read and follow the bold red text on the "Install SQL Patches" page...

... or better yet, for zc156 and later, just 'disable' the countries:

UPDATE countries SET status = 0 WHERE countries_id != 223;

or

UPDATE countries SET status = 0 WHERE countries_name != 'United States';

To disable all countries but the USA.

Hi,

I see that there were several suggestions provided for removing all countries except one in the Zen Cart forum. Could you please share which method you chose to implement, and more importantly, could you confirm whether it worked for your specific case?

This is indeed the recommended approach:

https://docs.zen-cart.com/user/admin_pages/locations/countries/#disablingenabling-countries