Have you searched the US Court Databases?
As an attorney - I have. Check out lexisnexis for case law. There are hundreds of cases of US owners of patents suing and litigating against international infringers... literally hundreds.
Also, you are totally discrediting the monopolies that run the world and how they have prevented other companies from entering their markets via other aggressive methods or patent purchasing...
Why don't you cite a handful of recent cases (<5 years) in which a British or German software company has been successfully sued in the US for infringing upon a US-registered software patent by a US patent troll? I'm not saying you're wrong, and of course just because I haven't found anything doesn't mean it doesn't exist, but the odds of being successfully sued by a patent troll as a foreign business are vastly less than being sued as a US company. Even if a patent troll were successful in securing judgment (perhaps by default), enforcing a judgment against a foreign company is vastly harder than a domestic one; patent trolls like easy wins.
Nobody in Europe is complaining about US patent trolls suing them because to the best of my knowledge, it doesn't happen. If it does, it's so infrequent that it's a non-issue.
I assume you're a troll because of your comment history. I mean, c'mon, you pretended to be able to read my mind and asserted that my lack of desire to open up an office or business in the US was not because of the risk and costs of a patent troll's attempt at a shake-down, but rather because I don't know how to form a company, or that I'm not a US citizen! If you're really a lawyer I doubt you'd be making such claims.