At one time your were correct but in recent years, power plant CO2 has dropped a great deal because Nat gas and renewables have replaced much of the coal formally used to generate electricity
Nope, you are misinformed. Natural gas has substantially reduced electric emissions, but not that much.
The most recent EPA data reports that emissions from electricity generation is 28.4% versus the transportation sector’s 28.5% of total US emissions. https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data
However, the transportation sector includes air, rail, ship, and pipeline modes as well as cars and trucks.
According to IEA “CO2 Emissions from Fuel Combustion” (2017), Figure 13, CO2 emissions from road transport account for about 75% of total transportation emissions. (2015 data)
Google for a link to this reference; it requires free registration.
So road transportation is only about 21% of the total.
But that includes heavy trucks, buses, and motorcycles as well as cars and light trucks. EPA’s latest “US GHG Emissions and Sinks, 1990-2015”, Table A-116, indicates that passenger cars and light trucks account for 71% of on-road vehicle emissions in particular.
So cars and light trucks in particular account for about 15% of total emissions. Not 28.5%. And that is using the latest available 2016 data for the EPA sectoral emissions and latest available 2015 for the split among transportation subsectors.
If you’d be happy with 2015 data, car and light truck emissions totalled 1.084 billion tonne CO2e (see Annex 3) versus the national total of 6.587 billion tonne, or about 16.5%.
https://www.epa.gov/sites/production/files/2017-02/documents/2017_all_annexes.pdf