If you want your site to show up for country-restricted searches, make sure it uses a country-specific domain (such as www.example.com.br). If you use a domain that isn't country specific (such as .com), make sure that the IP address of the site is located in that country.
If you want to know what visitors from different countries are searching for, take a look at the query stats in Sitemaps. This lets you see the difference in searches for each location, as well as what languages visitors use to type in their queries.
