Kostya Tszyu 13-2 (and a bogus no contest than should've been a win), 16 of his 34 combined fights were fought on foreign soil, 15 in the US), the rest in his adopted homeland Australia (2 of his early opponents were Australians) and he won and unified all his titles on foreign soil, both unification match ups in his opponent's home country.
Froch is 3 - 2 not great but at least he has fought and won outside of the UK. Taylor, Abraham and Johnson fights where won outside of the UK.
Mikkel Kessler 3-3? Its hard to accuratley quantify, because guys from countries like Denmark, leave for big fights...big fights=better fighters.
You also have to look at the quality of the fighters opponents. - Froch fought Kessler & Ward in their homecountry, lost close to Kessler and clear to Ward. Beat Johnson, Taylor & Abraham in foregin soil. - Mikkel Kessler lost to: Calzaghe, Ward & Froch at their backyard. Got cheated against Ward, but again no shame in losing to these three P4P fighters. He beat Haussler & Mundine at their backyards and beat a lesser opponent in Las Vegas. - Daniel Geale only has 1 loss vs Barker in Atalantic City. Beat Sylvester and Sturm in Germany, which says a lot. - Klitschko and Golovkin fights all over the world, they are not scared. No matter how you put it, european, british & australian fighters are more willing to travel and fight and fight overseas. American fighters could learn something here. Boxing today is not just an american sport, it has become a global sport.