Not only is the US sanctioning Russian banks and companies, but it also is trying to strong-arm European banks into enacting harsh sanctions against Russia as well. Given the amount of business that European banks do with Russia, European sanctions could hurt Europe at least as much as Russia. At the same time the US expects cooperation from European banks, it is also prosecuting those same banks and fining them billions of dollars for violating existing US sanctions. It is not difficult to imagine that European banks will increasingly become fed up with having to act as the US government's unpaid policemen, while having to pay billions of dollars in fines every time they engage in business that Washington doesn't like.
European banks are already cutting ties with American citizens and businesses due to the stringent compliance required by recently-passed laws such as FATCA (Foreign Account Tax Compliance Act). In the IRS's quest to suck in as much tax dollars as possible from around the world, the agency has made Americans into the pariahs of the international financial system. As the burdens the US government places on European banks grow heavier, it should be expected that more and more European banks will reduce their exposure to the United States and to the dollar, eventually leaving the US isolated. Attempting to isolate Russia, the US actually isolates itself.