Then point to numbers showing they have left in mass. If such a large part of manufacturing has left then how does the US (according the 2009 report linked) still lead the world in manufacturing output? Are productivity increases enough to make up for manufacturing leaving at the levels many people like think? I certainly don't think so.
Pointing to manufacturing jobs going away is an invalid metric to start. Manufacturing jobs are gone and going, but it's not something that can be stopped. Some jobs were moved overseas, but many have simply been automated away. Over time even the ones overseas will be automated away.
The point is that many US manufacturing industries have left.
The two points are different, especially for the workers who previously worked in those industries.
IE, the OP points that industries haven't left the US in mass. That the remaining industries are very productive is a different, etc.