Is it possible to search for users in a given country?
Of course you can only hope to find the users that have actually disclosed their location.
Not with the stock software on the site. But it should be possible with the data explorer. Given the goal of this query, it would be necessary to extract a list of all users in a given country. So you can probably edit the query's code to get what you want.
Note however that the code uses "location" as disclosed by the users in their profiles and a long list of
if...thens to assign major cities to countries. So someone living in New London, Connecticut, USA, and advertises his location as "New London, CT" would be assigned to the UK instead of the USA.