Russia is only doing this temporarily to cut prices for their own people. It's going to hurt Europe the most and it has already started increasing the prices on crude for the rest of the world. As soon as their own local currency is stabilized Russia will undoubtedly lift that ban. Without the money that the export of oil brings in, their country would be in deep trouble. I don't see how the world's second largest exporter of crude banning shipments would not increase prices for everybody globally, including the US.
*Disclaimer: I am not now and have never been an economist specializing in foreign/world affairs.