I think I already posted about this a while ago in this thread, but the Russian and American armed forces cannot be compared, as they're built for completely different things. The Russian army, like that of the Soviets, is almost completely centered around fighting a conflict either in Russia or in bordering nations.
You know how useful those large numbers of AFVs would be if the Russians went to war in, say, South America? It'd take months just to get a sizable portion of them to the opposing nation even if they could move them by boat, if they were fighting a landlocked country without Russian allies in the region, or if they were up against a superior navy, politics would probably find a peaceful solution before the backbone of the Russian armor got to its destination. And politics is never fast...
The US military focuses on strategic mobility because it has to due to its geographic location, and this means its extremely costly to use many AFVs, which are difficult to move by air and time consuming to move by boat. Hence, if a vehicle's role can be filled by a mixture of infantry and aircraft, it is.