Hi,
If you will see in the 'BuilContactStandardAddressRel' in genil browser then you will find that there is no field for country.
So Please give a try with below:-
I think you need to add a new attribute which can be value node attribute and then after getting the value from UI in this attribute you can use 'BAPI_BUPA_ADDRESS_CHANGE' to change the country for the contact person.
Thanks
Kumar