From The Guardian website reporting on an interview on BBC radio 4 this morning.

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Fauci says that US may not 'need' to use Oxford/AstraZeneca vaccine
US infectious disease official Dr Anthony Fauci has been on the media in the UK this morning, and said if safety concerns about AstraZeneca’s Covid-19 vaccine were straightened out it had good efficacy, but it might not be needed for Americans because of supplies of other shots.

“I think that the AstraZeneca vaccine from a standpoint of efficacy is a good vaccine, and if the safety issue gets straightened out in the European Union … the efficacy of that vaccine is really quite good,” he told BBC radio.

“The way the United States has made contractual relationships with a number of companies, we clearly have enough vaccine – or will get enough vaccine – that does not include AstraZeneca, which would be enough quantitatively to vaccinate everybody in the United States.”

Reuters reports that he added: “Whether or not we ever use AZ is unclear but it looks right now at this point in time that we will not need it. It’s not a negative indictment of AZ, it is just possible that given the supply that we have from other companies that we may not need to use an AZ vaccine.”

So far, 120.8 million people have received one or both doses of a vaccine in the US, and the Joe Biden administration has been keen to emphasise the speed at which it is being administered.
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I don't know how many AstraZeneca vaccines the US has in store rather than on order. Perhaps they might think about offering some of them to other countries now rather than later.