I don't think your last statement is correct. According to the linked page, the James H. Miller Jr. plant produces around 19 million metric tons of CO2 per year, while passenger cars produce around 760 million metric tons per year: https://www.statista.com/statistics/1235091/us-passenger-car...
Yes you are correct, my bad I was misremembering. It's the sum of the top 100 most polluting plants (656 million metric tons in 2020) which is close to the total emission of all passenger vehicles. It was closer in 2019, because 2020 saw a 10% drop in emissions due to COVID.