It's probably not going to bother Russia that much, as there were only about 10 to 15 troops training in the country, but it is the latest in a series of repercussions for Russia's actions in Ukraine. The U.S. has imposed economic sanctions and visa restrictions on those they believe are part of the decision to "undermine" Ukraine.
The real danger for Russia would be if the E.U. imposed sanctions, as it has a lot of Russian money. E.U. leaders have joined U.S. and NATO leaders in an attempt to reach a diplomatic solution to the Russian-Ukraine crisis before any more damage is done to any of the parties involved.
In an hour-long conversation with Russian President Vladimir Putin, U.S. President Barack Obama encouraged Putin to work on a solution that "addresses the interests of Russia, the people of Ukraine, and the international community."