OP - Several thoughts and a caution:
1. You need to make some decisions. Soon. Time is your enemy. With the cancellation of your scheduled flight, other pax on that flight will be rebooking onto the earlier / later flights and soon enough (if not already), there won't be 4 seats to be had. You will then be stuck somewhere for some period of time.
2. The PHX conenction is legal. If you misconnect, US will rebook you next available. That is because it is "day of" and US will be the late-delivering carrier. Right now, CX is the ticketing carrier and it is CX which needs to deal with US. The unknown here is what "next available" means.
You are simply going to have to do an analysis, including determining what your travel insurance will cover here, and come to a decision.