Okay, so Rebekah TJLC Explained has suggested that most of the stuff Mycroft is involved is in Asia, but I think, not all. He "wades in" to Serbia, and he obviously involves himself with Magnussen, who is European, has well as issues of "national" importance, like the Bruce-Partington plans. Perhaps he is simply involved in issues of surveillance and "secret states"?
...except that both Holmes brothers-- as Irene Adler knew-- care rather more than they let on. I suspect it's why she sought them out as her best bet, given everyone else who was after the information on her phone.