If Russia and the US had a war who would win?

It would be 50/50 depending on where it was.

Assuming the war did not go nuclear, the United States has the most technically advanced military giving them a big advantage in conventional war, however, it really depends on who attacks who first. Regardless of which, the war would be enormous. It would easily dwarf WWII and the lives of Americans and Russians would greatly be changed. It would not be hard to assume that a large majority of the invaded population would be killed. And in the case of the United States, a loss of democracy and an installment of a police state that would be hard to get ride of for years to come. Due to the fact that liberty would be dropped to help the war effort such as the draft, limitless president terms etc. think of the Patriot act but 10 times more so. It would be a reasonable prediction that the US would win the war (don't forget US allies such as NATO), but it would be an extremely heavy pyrrhic victory. So much so that the country wouldn't really even be the US anymore but something new. To put it blunt there would be no winner.
Advantages/Russia
Russias biological Weapon systems out number U.S. and Russias tanks,helicopters,vehicals outnumber U.S's

Advantages/U.S.
U.S's infantry are highly trained,so as helicopter pilots,tank drivers,vehicals and any plane fighters are convoy pilots.
U.S. technology is greater then Russias.
U.S. has more task force specilized armed fources then Russia.
U.S. has more allies like,Canadian armed fources,UK armed fources,Europe specilized task fource.

Although it depends where the war happends.if Russia attacked unknowingly U.S. would have a devastanting critical hit.(CoD MW2)even if so U.S. armed forces and the natinol guard would be alerted before Russia would even get to fire one round on U.S. soil. task forces would be alerted,allies would be called in and Russia will probly be flanked from all directions.

if U.S. attacked unknowingly they wouldent do it in fource(probly like Russia would)they would send in U.S. navy seals to one side and send in task forces to wipe all natinol defence then come in like WW but risk surrounding countrys.

if they did use nukes the whole world would turn on either country who started the war.