Yes, you can easily map social profile data from Facebook into your custom fields in JomSocial. You'll be able to map the desired fields and (if automatic registration is disabled) configure how this imported data will be shown during the mini-registration process.
* If you'd like more information on how we integrate with JomSocial, you can see
this page
* If you'd like to see the step-by-step guide on how to do this, please view our
Initial Configuration Guide
for how to set up the Social Profiles plugins/section within JFBConnect.
Since you specifically mentioned Country fields, I do just want to point out that the location field returned from Facebook is no longer broken out into City, State, Country, etc as it once was, but is instead just a single Location value.
I hope this answers your questions, but let us know if you need more clarification.
-Melissa