For those that lost rankings in country A but kept traffic in country B, C or D. Some ideas for possible factors.
1) Was your page targeting a certain country (WBT Geo targeting)
2)Where was hosted
3)Which country had more visitors
4)Did you had pages written in other languages
5)Finally one of the major factors IMO is how long visitors spend on your site, clever link structure that force the visitor to click on different areas of your site to get more information.