Both French and Japanese HSR were/are financial black holes that bankrupted the relevant railway companies. French TGV is nice but again, stations are often far outside the city centres. Compared to flying (profitable on its own) it's not at all clear any of these countries made the right decisions.
WRT CO2, it's not quite so clear cut unfortunately. Planes emit more only because they travel further. Mile for mile they aren't that different these days.
Only if powered entirely by non-emitting power sources, which requires you to assume nuclear power creates no pollution. Not much CO2 I'll give you that, but no pollution, not the case.
If we were to be in a debate class, and you were assigned to argue in favor of electric trains, I'm sure you would point out that in a single month California build more than enough solar capacity to power all 16 trains for the Phase 1.
Every month for the next 5 years, California is projected to build an average of 250 MW solar (15 GW overall [1]). The highest power TGV: 12.24 MW [2]. It's in fact enough to power 20 trains.
WRT CO2, it's not quite so clear cut unfortunately. Planes emit more only because they travel further. Mile for mile they aren't that different these days.