> There isn’t a ton of goods that need to get between LA and Seattle, say.

I don't know if that's really true. There's not enough to justify Jones act ocean shipping between those ports, because rail and road are viable. But ocean shipping vessels routinely stop and both ports on one voyage and if they could legally transport cargo between US ports, I expect they would.

There's a lot of trade in physical products between Washington and California. Agreculture and aerospace are a big part of both economies.