if I’m going from California to New York

Yup, that's like 70-80 hours, depending on where in CA you're leaving from. So you'll be on that train for 3 days, and have to change trains 2-4 times. The plus side is that it's cost-competitive w/ flying ($400-ish, vs $200-ish flying), but that's for coach, so you'd spend those 3 days sleeping in a chair. If you want a sleeper room, that's like $2k.

A direct flight would take 5-ish hours and cost $200-ish.

There's a reason nobody rides trains in the US, and it's because it takes way too long and it's too expensive. It would be a fun experience, but not great if you're using it for transportation.