Not sure where you're getting your data, but it's incorrect.

It was not considered a failure. There have been some questions about what the best dosage and timing might be for the highest effectiveness, but I've heard the UK may approve it as early as tomorrow.

The USA may wait until the trial being run inside the USA is completed, but that has more to do with ensuring the vaccine is safe and works on their wide demographics than any concerns with how the UK and Brazil studies were done.