Do couples sign visas to the United States together or separately?

It is best to apply for a visa together.

I suggest that you apply for a visa together, because even if you go to the suburbs, let alone go to places so far abroad, whether you are traveling alone or with a group, you will definitely go with your relatives and friends. So in order to avoid this unnecessary rejection, I suggest you go with your relatives and friends, such as your parents, brothers and sisters, friends or colleagues. They sign with you just to improve your visa pass rate. If you sign, you don't have to go. It will take many years anyway.