I'm told the huge difference in the size of us and soviet tanks is largely because soviet planners sat down, looked at the parts of Eastern Europe the tanks were intended to operate, and said "we must keep the weight of these tanks below the maximum weight the bridges in this are can handle".

The US did not do that, and combined with MIC inefficiency and excess we ended up with very heavy tanks that while powerful had a questionable ability to actually manuever in their intended environment.