Why doesn't single payer healthcare work above 60 to 80 million people?

I'm thinking it becomes just too encumbered and has too many details to properly function and so becomes actually counterproductive on all levels at once. It would be sort of like building a plane too big to land at any airport, for example. It might fly 1000 or even 10,000 people at once but the airplane couldn't land anywhere ever except to crash land into the ocean.

As a result the only single payer healthcare system that could work for everyone would be state by state here in the U.S. because no Federal program could work that covered everyone.