This is the reason why country fields are not being passed. This is the right answer.
Every picklist has an Option Name and Option Value.
Option Name: The name that is displayed in the user interface
Option Value: The actual value of the picklist
SCENARIO-1
Eloqua
Picklist Name : Country
| Option Name | Option Value |
| United States of America | USA |
| Canada | CA |
| United Kingdom | UK |
salesforce
Picklist Name: Country
| Option Name | Option Value |
| United States of America | USA |
| Canada | CA |
| United Kingdom | UK |
Action: Eloqua passes the Option value to Salesforce
Results: Both Eloqua and salesforce Country picklists have the same Option values, So the option value is accepted by salesforce and it is displayed in the User Interface.
SCENARIO-2
Eloqua
Picklist Name : Country
| Option Name | Option Value |
| United States of America | USA |
| Canada | CA |
| United Kingdom | UK |
salesforce
Picklist Name: Country
| Option Name | Option Value |
| United States of America | United States |
| Canada | Canada |
| United Kingdom | United Kingdom |
Action: Eloqua passes the Option value of the pick list to salesforce
Results: Eloqua picklist "Country" and salesforce picklist "Country" have different Option Values , in this case the value is not accepted by salesforce.
Solution
The best practice would be to keep the same option values of picklists in Eloqua and salesforce.
Hope this is clear enough.