I am wasting my time post PhD due to delay in immigration documents processing. What to do? Please advise
Get off the couch and go workout.  
If you are not 100% proficient in English, study it to complete fluency.  
Get in the lab (or whatever) and do some papers.  Use the Pomerado to motivate yourself.  Impossible to goof when that tomato is running. 
Remember, you shouldn't need your advisor to push you.  Especially as a post-doc.  You are supposed to be a budding PI. But, since you are struggling, at least show up and talk to her (or Zoom or whatever).


As for your visa problems, this is irrelevant. You have your Ph.D. Getting an immigration document will not or not should not change your competence, work ethic, maturity, etc.