How can I mass edit country or city values of many contacts?
Profiles are used for so many unrelated things that it's kind of ridiculous.  Here is the minimum needed to bulk edit country for a bunch of contacts.


Create a new profile.  Don't worry about any of the settings besides the name, which you might call "Country Update".
Once you save it, you'll be shown the New Profile Field screen.  For Field Name, select Contacts, then Country, then Primary (or whatever location type you prefer).  Don't worry about any other fields, and click Save.


You now have a profile with a single field in it--the field you want to bulk update.  You could potentially skip these steps by using an existing profile with Country in it.


Search for the contacts you want to update.  Check the boxes or select all records (the maximum to batch update at once is 100, and they have to be the same contact type--individuals, households, or organizations), and select Batch Update via Profile in the Actions drop-down.
Find your "Country Update" profile in the list, and select Continue.
You'll see the list of contacts and a field for each contact's country.  To set them all in one go, set the first contact's country, and then click the copy icon in the header.  That will copy all the way down the column.  Click Update Contacts, and you're done.


Once you get the gist, you can set up more complicated profiles and set multiple fields in one sitting.