Change the navigation ul li based on the clicked country
From a once over:


Using each seems overkill, this works:

$.fn.myWidget = function () {
    this.click( function (e) {
        if (e) {
            e.preventDefault ();
        }
        combine_all(this);
    });
};


This code assigns the same function to all elements in this, the function has this as the clicked element, so that is why you provide to combine_all
JavaScript uses lowerCamelCase so combine_all -> combineAll, also combineAll is not enlightening as function names go
Your code is repetitive to determine the links, for starters you could do something like this:

var country_links = {
  uk     : [ 'UK stuff', 'UK phones' ]
  europe : [ 'EU stuff', 'EU phones' ]
  italy  : [ 'Italy stuff', 'Italy phones' ]
  germany: [ 'Germany stuff', 'Germany phones' ]
};

 this.updateNavigation = function(my_region){
      var oldNavigation = $('#navigation').find('ul'),
          menuItems = country_links[ my_region.split('_')[0] ];
          newNavigation = '&lt;ul&gt;';
       for( var i = 0 ; i &lt; menuItems.length ; i ++ ){
           newNavigation += '&lt;li id="menu-' + (i+1) + '"&gt;' + menuItems[i] + '&lt;/li&gt;';
       }
       newNavigation += '&lt;/ul&gt;'

      $(old_navigation).hide().html(new_navigation).fadeIn(800);
 };


This is not the only approach, but you split data from style, country_links has all the data. updateNavigation knows how to build a list from that. I did not test this code but you should catch my drift.
To finish on the first point, I would just call all three functions on top instead of combineAll