But, given how grave and urgent the situation is getting, there is no way to convert all curent energy generation to green energy AND increase energy generation capacity to keep up with normal economic growth AND increase it many times over to electrify all transportation AND electrify all heating. And even if we were to succeed in all that, that only covers about half of US emissions at best - the other half is coming from agriculture, industry and residential emissions. Not to mention the massive emissions that are happening in China but ultimately serving the US market.
It's simply not possible to achieve the necessary time frames (net 0 in 20 years) without significantly reducing economic activity and standards of living in the short term - then growing back to current activity and standards of living in the longer term.
> But the US could go to zero and if China and India don't lower emission it won't matter.
Because if the US cut its emissions by half, the standard of living of US citizens (and its associated carbon cost) will become about the same as in China, and will still be a whopping 3.5 times better than India.
Looking at total emissions is actually meaningless, as reducing emissions (significantly) necessarily involves lowering the standard of living - less meat, less transportation, more expensive electricity, less stuff, less construction, less heating etc. The US and EU have a lot of place for reducing our CO2 by reducing our standards of living than India (which produces less CO2 per person than Sweden or any other country in the EU).
Sure, there is some amount of CO2 reduction that can be achieved by green power, but nowhere near enough at the scale and speed needed to avoid catastrophic climate change.