Hi John, I’m affraid JR Pass is only for visitors on a Temporary Visitor Visa, which is given if you enter with the purpose of tourism.
As a European citizen, I’m not to familiar with what a “US Official visa” is exactly sorry – but if it’s for tourism, you should be able to exchange. If any other purpouse than tourism, then no.
Its’s important it’s for tourism, becuase that’s the only visa which provides you with a special sticker / stamp in your passport which is required to exchange and activate the JR Pass.
Most visitors who enter Japan will be given a 90 days temporary visitor visum upon arrival, it’s almost concidered visa-free as you don’t have to apply for it beforehand in most cases.
Hope it was of help and have a wonderful stay in Japan!
With kind regards, Jonathan H.