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.