If US were to ban ICE cars and truck and switch go horse-and-buggy tomorrow, it will save 29% of US emissions. US accounts for 15% of global emissions. Thus the overall global savings will be 4.35%, or about 1.44 GT CO2/year. Fantastic. Yet 95.65% of emissions will still be going out every year. In 20 years, emissions have grown from 25 GT CO2/year to 36 GT CO2/year, or about .5 GT CO2 / year. The whole 4.35% savings would turn out to be a minor blip, overtaken in about 3 years by new emissions elsewhere in the developing world.
We are already 40+% above Paris agreement 1.5C emissions levels of 25 GT CO2/year. We need deep cuts on massive scale. If the world were even remotely serious about tackling CO2 emissions for a rough but perhaps survivable crash landing, we'd see:
* World wide moratorium on building new coal/gas/oil power plants and ICE vehicles.
* World wide moratorium on economic growth. Good bye lifting the third world out of poverty. Good bye western retirement.
* Gradual phasing out of industry in developed countries. Good bye middle class lifestyle.
* Ban of immigration from low emission countries into high emission countries.
https://www.c2es.org/content/u-s-emissions
https://ourworldindata.org/co2-and-other-greenhouse-gas-emis...