I am currently in US with student visa, so probably going to work on F-1 OPT. Yes I have seen someone posted in this thread working on J-1 visa. I'm not sure how difficult it is procedurally, but I know that many postdocs (with or without US PhD degree) can work with J-1 visa. I also know a few international students work on F-2 or J-2 or H-4 in US (if you are married). Is it possible to apply for RA jobs in Europe?
Hopefully interviews are not done yet, and sometimes people can get an offer in March or April even without an interview. Good luck!
(Now I have 2 rejections and 6 silent applications... It's probably theoretically too early to give up, but maybe I should consider alternative plan. Actually feeling better now)