The Hungarian and Czech government never called onto US troops to put down demonstrators - what kind of history books did you ever read?Stalin and the following Soviet-leaders controlled or as you prefer "enslaved" Eastern Europe, just as much as the USA controlled "enslaved" e.g. Germany and Japan after WW2.
How many Hungarians were killed by US troops in 1956?
How many Czechs were killed by US troops in the Prague Spring?
BTW - around 100 Czechs were killed by Russian troops. And an estimated 2000 people in the Hungarian uprising.
However the US occupied and controlled South Korea, and it's "democratic" government killed around 2000 pro-democracy students and civilians during a 3 day demonstration e.g. Kwangju in May 1980 - what did the US Army or government do? - nothing - but kept their Puppet in power till 1988.