Russian energy a threat to Europe, but not the US

As a major natural gas producer, Russia may be able to threaten Europe with winter supply disruptions in the midst of the Ukraine crisis, but that leverage doesn't extend to the United States. And any pipeline disruptions in Ukraine would affect some parts of Europe worse than others.

Unlike oil, which is shipped via tanker and priced globally, much natural gas consumed in Europe is shipped by pipeline and priced by Russia. It often travels through Ukraine. That leaves Europe exposed to any supply disruptions in Ukraine or any use of natural gas by Russia for political leverage.

"This doesn't directly affect the United States, which is not part of any of these pipeline networks, and does not buy any (liquid natural gas) from Russia, either," said Olga Oliker, associate director of Rand Corp.'s International Security and Defense Policy Center.

Russia's actions 'pre-planned': Pro
Russia's actions 'pre-planned': Pro

Ukrainian supply disruptions also potentially would be a more immediate problem for Eastern Europe than for Northern Europe. As the map here shows, Ukraine acts as a conduit for pipelines going to Poland, Hungary, Romania, Slovakia and back into Russia. In contrast, Germany for example can access Russian gas via pipelines running through Poland and the North Sea.

All that said, Europe is generally less reliant on Russian natural gas this year than it was in previous years, thanks to a mild winter and solid gas supplies that are already in place.

(Read more: 'Nazis' and 'hypocrites': What Russia's saying on TV)

"In the current crisis, Europe has substantial gas stocks, and Ukraine (which is a major customer of Russian gas as well as a transit state) has also been buying up gas," Oliker said. "But stocks won't last forever."

By CNBC's Ted Kemp. Follow him on Twitter at @TedKempCNBC. CNBC's Patti Domm contributed to this report.