How to match a form of a country to an address field?

How to match a form of a country to an address field?

This is the scenario

1. I have a country form to create list of countries
2. I have product  with lookup for country
3. I have user form that has address field

how can I show the products with the country that matched the user? 
I need to know how to code it and also just by using the report filter. 

Thanks