An American entry along side HAAS will be high on the Liberty agenda to get more US fans on board the F1 train.
I can't see a single existing team embracing a new team as it just waters down the broth a tad more that they all depend on.
Haas doesn't FEEL like an American team to me. I know that Gene is American, but to me feels like he's just slapped his name on an Italian team. Nothing wrong with that, Red Bull, Mercedes and Alpine are all English teams racing under other flags, but I don't pretend that their victories are Austrian, German or French.
If I had to pick an 'American' team, I'd go with McLaren. I know they've got a long British racing heritage, and they're named for a Kiwi, but Zack Brown is about as American as F1 gets these days. McLaren is actually invested in American racing, and understands that the American audience is up for grabs, both in terms of racing fans and purchasing fancy cars.
Of course, 'Andretti' is is the most American name you can have in (open wheel) racing.
Andretti has the history and ability to be that team and it would be a good thing for F1 to bring in some new blood. They can bring GM in as an engine supplier which will also give current teams another choice for powerplants.
Running an IndyCar team is a far cry from running an F1 team. But there's nothing like running an F1 team except running an F1 team. It's not a natural step up. All the same, Andretti is going in as wide eyed as possible. I feel like they'll have good will from sponsors and team personnel to get them over any rough patches.
GM has a history in Le mans but to my knowledge have never been involved in F1.
Ford on the other hand totally screwed the pooch when they took over Stewart GP and showed everyone that you can't operate an F1 team from a corporate boardroom across the pond.
Running a team by committee does not work.
Honda and Toyota also suffered the same fate as Jaguar. Alpine is making the same mistake now. Mercedes fully understood they're slapping the name on the car, signing the cheques and leaving the rest to Toto. (Much like Gene does with Haas/Steiner I suppose)