Or - and hear me out here - the US could invest in their public transportation infrastructure. But sure, let's do flying taxis.

Flying taxis is public transportation

Charging $3 for bus riders is controversial within the public transportation sphere, nevermind the $20 a car taxi can cost. Unless there's something about flying taxis that would make them price competitive with a $3 bus trip, it's hardly public transportation.

If there were automated and electricity was cheap its easy to imagine them being cost competitive vs a bus trip of the same distance just because they're so much faster. Making them price competitive is just a matter of how much the state is willing to subsidise them.

They are only faster because we refuse to build infrastructure for public transport. A Bus rapid transit system using one dedicated lane of traffic can move up to 30k per hour. Maybe we should use automation to build efficient public transit, instead of imagining hundreds of millions of private automated cars clogging the roads and robo taxis flying over those clogged roads. Build some light rail and buses with dedicated lanes, and use automated 4 passenger vehicles for “first mile, last mile”.

No they are not. Taxis aren't public transport either.

This CityAirbus takes what, 4-6 people seated? A bus easily takes 40+, a tram 60+ and a metro 250+* - and that's just seats, they all fit hundreds of people if you include standing passengers.

It would take ages and hundreds/thousands of flying taxis to clear a stadium, while it takes only tens of metro trains.

* Numbers taken from public transport options in my home town, will of course differ around the world

Taxis are not mass transit, but they are public transport per the definition.

Obviously this will not be comparable in capacity to a metro, but it can conceivably be comparable in capacity to bus lines which tend to operate at very low load factors in US cities, by virtue of being much faster to complete the same journey.

I'm not going to argue with you about the different definitions of public transportation, but for sure "taxi" isn't what comes to mind when someone mentions public transportation.

The point you're making is exactly the problem. The reason bus lines aren't used more is because they suck in a lot of cities. Improving the public transportation infrastucture (and no, not taxis), would solve this problem - as demonstrated in many European cities.

Here's a good video that compares the city planning of Houston to other cities, and explains why it sucks. It focuses more on cars vs. bikes, but the same basic point also applies to public transportation: https://www.youtube.com/watch?v=uxykI30fS54

At four people per vehicle, I doubt that you could achieve anything like a satisfactory throughput in this scenario, given reasonable traffic separation. Unloading will be one bottleneck, as each vehicle will need as much space as several buses, when you take into account sufficient separation to avoid unsafe aerodynamic interaction.