Car transfer from Rome airport FCO to Assisi

https://www.rome2rio.com/s/Rome-Airport-FCO/Assisi

That’s a 2.5 hour drive
I figure based on other shorter transfers we’ve done it will cost at least 400 euros?

You might check mydaytrip.com

That's probably not going to be a "cheap" trip.....

https://booking.jayride.com/find?from-type=airport-terminal&from-description=Rome%20Airport%20(FCO),%20Terminal%201&from-lat=41.795172&from-lng=12.254845&currency=EUR&passengers=1&to-description=06081%20Assisi,%20Province%20of%20Perugia,%20Italy&to-type=others&to-lat=43.0707017&to-lng=12.6195966&datetime-local=2022-04-28T10:00

If you have a generous travel budget, that's certainly an option. I always tough it out and take the train.

after a long flight from the USA it might be nice to just get in a car and ride.

Train would be more spacious

I'll vote for the train too. After being stuck in an airplane for hours, it would be nice to be able to get up now and again and take a stretch? You'd also have restrooms at hand.

I'd check the Trenitalia website for actual train-journey times and options versus Rome2Rio.

Thanks everyone. Yes we decided to take the train. We've done it before but since our arrival time is early was just exploring. We'll save some money to spend on some really great Umbrian dinners.