That isn't true about private automobiles and I would be interested to know where you have been hearing it. It must come from some party with a vested interest in making car emissions seem like a non-problem. In reality, car emissions are the main thing that Americans and most other rich countries should be trying to address.

Here's a graphic of the latest data available for California, as an example: https://ww2.arb.ca.gov/sites/default/files/images/2023_scopi...