I don’t see this as nearly the same as saying Trump is Biden is Trump. If I have to fault Stewart here, it’s that he didn’t have the foresight to understand that Trump would set about immediately destroying the country through chaos and confusion. To be fair, not many people outside of me were saying exactly that.
But to break down what he’s saying above, it reads to me as, the institutions are strong enough to keep this country alive even if Trump is elected, and just electing Biden isn’t enough by itself to save the country and make the Trump problem go away. Criticize Stewart for the first point as you like, but even you have to admit he’s right on the second point.