Kavre, I don’t think they need any sponsorships. Even if you send it , they do not look at it. But no harm in trying. Long time back I send for one of my friend , they did not look at it. I just has simple letter stating that I will support him. No affidavit of support. He got the visa as he was working for Nepal army and station in Congo for UN mission. FYI, US embassy has not open visa B1/B2 visa unless it’s emergency.