I hope United States can send the vaccine to other countries because I heard that many countries are waiting for the vaccine distribution. If the United States can do that, many people from different countries can get help and get vaccinated as soon as possible. That can reduce the number of people who can get infected because they can be vaccinated at the right time, saving more lives. It will be good news if the United States can give a lower price to the country that needs the vaccine.
At this time, when most of the countries are facing an acute shortage of the vaccine, it is unethical and immoral to hoard the vaccine doses. I don't understand the point in hoarding the vaccine doses (such as those AstraZeneca), if they don't intend to use them. And let's not forget the fact that the US government had imposed an embargo on the export of raw materials needed for the production of the AstraZeneca vaccine to India, which made the second wave of COVID 19 much worse in that country.
This is how powerful countries ensure that the pandemic stays long enough. There is an excellent video on this by VOX on Youtube. You can check the video
here. It explains the reason why countries like the USA,UK and others are hoarding vaccine. It also explains the economics of hoarding and the benefit it will bring to them in the future.