If I had to guess: "You are a machine." It's reminiscent of Victorian authors describing the heart as pistons or the brain as strings being pulled. Less of a fact and more of a metaphor, a poetic interpretation.
Then, add on the entirely subjective experience each of us has of consciousness: it's not obvious that subjectivity is created or come from machines. Each of us has one good example, and the rest is intuition, induction. At best, "You can build machines like us, because we ourselves are the proof," is a wishful project, rather than a proof.
I think your definition of a machine is limited to simple mechanical devices.
Machines are just physical systems that perform some work. This includes cells, biological systems etc
If we built a human from scratch at atom level detail then it would be reasonable assume it would experience the world as we would. By definition you would have created consciousness.
The issue isn't with machines, but humans as just machines. You rightly point to the assumption: "If we built a human from scratch at atom level detail then it would be reasonable assume it would experience the world as we would." What's the reason the clone has to have experience?
I'm not sure whether this clone would or not, but we don't have a good basis for either. If we built one, we should act like it does experience things, but that's on moral, not scientific grounds.
Then, add on the entirely subjective experience each of us has of consciousness: it's not obvious that subjectivity is created or come from machines. Each of us has one good example, and the rest is intuition, induction. At best, "You can build machines like us, because we ourselves are the proof," is a wishful project, rather than a proof.