Germany, Russia, & the Ukraine
If the response to the Russian incursions in the Ukraine are economic - another way of saying impose sanctions rather than sending troops - it's Germany, not America, that will be the key player. Whether Germans want that role or not.
Russia is, at best, a minor trade partner with the U.S. - one reason that it's easy for Putin to use his caricature of America as a straw man to prop himself up. Germany, on the other hand, does significant trade with Russia. The relationship is certainly symbiotic - Russia supplies 30 percent of Germany's natural gas, according to some estimates - but given Russia's present economic shape, Germany has far more leverage than it seems ready to use.
In the years since the end of the Cold War - and more importantly the reunification of the country - German policy toward Russia has been mostly one of quiet engagement and occasional accommodation. That made sense in the immediate aftermath of the breakup of the Soviet Union; it helped encourage democratic reforms. But that period has ended - and in fact ended with invasion of Georgia by Russian troops in 2008. Indeed, it was that incident and the tepid Western response that in many ways set the stage for the present crisis.
To apply economic pressure, Germany and the rest of the western European countries have to do more than simply freeze a few bank accounts. They have to make a serious dent in Russia's revenues. A significant drop in oil and gas revenue would threaten Putin's regime far more than a democracy movement in the Ukraine; if you're going to apply economic pressure on him, that's how to do it.
The real problem is - what happens then? Does the West (and here the U.S. is a major player along with Germany) really want to take responsibility for the Ukraine's economy?
Call me cynical, but I don't see that happening. Just as I don't see Germany cutting its Russian gas purchases by twenty-five percent any time soon.