In WWI, American military was so bad even Euro military didn't want their help, while 20 years later in WWII American military were basically one of the best (Germany Army was best) in the world. Russian Red Army was not so strong without American's military/economic supports (Stalin said it's impossible/imaginable to beat Germany without American's help). American keeps best military until now and we all know Russian military are so bad and has nothing except nuclear weapons.