https://www.epa.gov/greenvehicles/fast-facts-transportation-...
From those figures, the entire civil aviation sector accounts for 13% of European transport emissions and 8% of US transport emissions. I can't find a breakdown of GA vs. airline, but I highly suspect GA to be a small fraction of civil aviation emissions relative to airline.
Be concerned about activities that make up the majority of emissions: passenger vehicles, electricity generation, and industry. Eliminating GA tomorrow would barely make a dent.
In fact, leaded aviation fuel is the largest source of lead emitted to the atmosphere in the US.
Eliminating GA tomorrow _would_ make a dent on the lead exposure of those who live near GA facilities.
See this study that attempts to quantify the damage done to IQ because of this additional lead: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338738/#:~:tex....
I live in the flight path for a small field that had been a round for a long time. Soil lead levels are very low here. I have no concerns about the atmospheric amount either. The biggest source of exposure for most people is likely food.
Also, civil aviation emissions have larger warming impact than just the CO2 emissions would say, as the radiative forcing effect is dramatically multiplied due to what happens high in the atmosphere - see eg https://csl.noaa.gov/news/2020/287_0903.html
(May not apply as much to GA due to lower altitudes and/or combustion properties of different fuels and engines)