The US would collaborate with China on this if it would make financial sense. It could even be an opportunity to straight things out a bit.
That being said, I agree that it's not going to happen. First, Tianzhou is currently cargo-only, for which there are enough alternatives. Second, the US is close to getting back their own human access to space (through Boeing and SpaceX), and that would probably be ready before sufficient restructuring & testing on Tianzhou is completed.
Edit: Shenzhou is the human rated version of Tianzhou, so the main question would be whether it can dock with the ISS. (There's not just the dock itself that has to fit, but there's additional limitation on what kind of maneuverability system can be used close to the ISS). Also, the next Shenzhou flight was originally scheduled for 2018 and got delayed to 2020 - so this is highly unlikely going to be an option (No Mark-Watney-style rescue is required unless the docked Soyuz modules are 'grounded' as well)
That being said, I agree that it's not going to happen. First, Tianzhou is currently cargo-only, for which there are enough alternatives. Second, the US is close to getting back their own human access to space (through Boeing and SpaceX), and that would probably be ready before sufficient restructuring & testing on Tianzhou is completed.
Edit: Shenzhou is the human rated version of Tianzhou, so the main question would be whether it can dock with the ISS. (There's not just the dock itself that has to fit, but there's additional limitation on what kind of maneuverability system can be used close to the ISS). Also, the next Shenzhou flight was originally scheduled for 2018 and got delayed to 2020 - so this is highly unlikely going to be an option (No Mark-Watney-style rescue is required unless the docked Soyuz modules are 'grounded' as well)