The Americans then went ahead when Paul Stastny scored his second by firing a wrist shot high into the net on a powerplay but it took 36 seconds for Kovalchuk to draw the Russians level.
In the second period United States defenceman Matt Hunwick's slapshot from the blue line deflected off a Russian stick into the net before Russia leveled again through Alexei Tereshenko.
Yevgeny Medvedev then put Russia ahead when he drilled a loose puck into the net with just over six minutes left, before Radulov fired home Kovalchuk's pass to wrap up the victory.
Russia top Group B after three games, one point ahead of Finland with the U.S. a further two points off the pace.
In the early game in Helsinki, Austria turned on the style to beat Latvia 6-3 and climb to sixth in the Group B standings, leaving the Latvians firmly rooted to the bottom of the table.
In Group A, Canada hammered Norway 7-1 with Steven Stamkos notching a goal and three assists in Stockholm.
Canada scored four goals - three off Stamkos assists - in the first period to take control and never looked back while Norway managed only one shot on target in the opening spell.
Canada are second with seven points from three games, one point behind Switzerland and a point above Sweden and Norway.
Denmark moved off the bottom by leapfrogging Slovenia who they beat 3-2 with Morten Green grabbing the winner in overtime in the early game in the Swedish capital.
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