Well done, overall it's a good solution and design is good.
What i realized is that the website might not be too accessible, the countryCards are not focusable by keyboard tabbing so you can only tab upto the dropdown list. It seems you might need to use an anchor tag to fix that issue.
Also in terms of routing I see you used '/search-result' for showing the extra details of a country, but I think you could have used dynamic routing so that each country has its own unique link. I think that doing so would also make it perfect to include the anchor tags.
I also realized that when you changed the regions, the cards are no longer clickable, idk why that's so and I wasnt able to inspect your code because you might have uploaded the incorrect github repo url(Rock Papaer Scissors).
In terms of the search feature, you made it so only when the user types in the full spelling of the country can they actually find it, so what if I can spell the country im looking for? I don't remember if it was required but for my solution when you type it changes realtime for all the countries that matches the user's search query. So they wont have to have the full name of the country.
Another issue is that when you have opened the extra details of the country, you should also make the border countries navigable so when a user clicks on it, they can get instantly directed to that countries page.
Finally for the mobile design for the countries details page, it seems like you just centered align everything there so you could also fix that up.
Overall this was a good effort and you did well attempting it.
Have a great day.