144 hour visa?Would I be able to use the 144 hour free transit or no?

I am a US citizen and considering a flight from US connecting through Europe to Shanghai. My return would be Shanghai direct home to US. Would I be able to use the 144 hour transit visa or no? Technically, I would be traveling from the UK-Shanghai, then Shanghai-USA but my originating flight would be from the US. Or, would I need to fly to the UK and overnight in order to qualify??