Comment by tmnvdb

The obvious answer is that the US is still a democracy with free media and rule of law. That means you're likely to be found out and have a huge scandal if you try to use government resources to manipulate the public at scale. This is somewhat confirmed by the huge scandals causes by relatively small scale manipulations, which form the somewhat worn examples commenters on this website like to bring up whenever criticism of China is voiced. Note that in China there is no such risk of discovery or pushback as media and courts are fully controlled by the Chinese Communist Party.