Is the US using bank fines to bring allies into line against Russia?

Here’s one for all you conspiracy nuts out there, prompted by readers’ comments on my recent item about whether BP has been unjustly targeted by the US political and judicial establishment. I gather there’s a theory that the hounding of non-US banks by the US Department of Justice for sanctions-busting and trading misdemeanours has a more sinister foreign-policy impetus behind it.