So I haven't used it internationally, but I came back to report that the app is working much better for me now. I went on a business trip last week and had default payment set for uber cash. It used the cash, the amex credit and then asked me if I wanted to buy more credit at a discount or just cover the trip. I used it multiple times just buying enough cash to cover the trip and it asked me correctly every time. Sounds like there are still some edge cases out there for international and for some other instances, hopefully we are headed in the right direction.