What does it mean "English proficiency" for a J-1 visa? English is not my native language. Meanwhile,  sometimes  I should read and write in English due to various reasons and work duties. In most cases, I understand a lot of (approx 80% and more) from the newspapers and other articles without a dictionary. The main idea and specific moments understand without serious difficulties in listening to different conversations or TED talks. I don't know my exact CERF level because I have never passed the corresponding exams before. Meanwhile, I have passed through the interview with PI in a US university and got an offer, so my English is acceptable for them probably.  However, speaking fluently is difficult for me (I have not had enough practice for the last two years), especially when a topic does not link with work. Sometimes seem that the current speaking problem is due to a long break.
Now I am preparing for the J-1 visa interview, where &quot;English proficiency&quot; is one of the requirements, and I am a bit confused by this moment. What does it mean &quot;proficiency&quot; for an embassy officer? What should it be minimal CERF level?
Sometimes I am sure I will not have got the visa due to my English ((
Candidates must be proficient enough in English to participate successfully in their exchange program and to function on a day-to-day basis. J-1 Exchange Visitors must have sufficient, verifiable English language skills.
The CEFR Common European Framework of Reference for Languages is a European certificate. Notice that it's CEFR level, not CERF.
In the US, they expect a TOEFL certificate or equivalent (like SAT or Pearson tests). An acceptable grade for some programs in the internet based TOEFL would be 79 points, which is the equivalent to a B2 level in the CEFR.
There are sample tests online that might help you get an idea of your present level. For example, this one. However, judging by your post, I assume you are at a more than acceptable level, probably at the C1 or even C2 level.
PS: I have the impression that you believe it's the US gov who is setting the English proficiency standards. Actually, it's the university who sets the standards and how to prove proficiency. If the university accepts you I don't see how the government can reject the J2 application for lack of proficiency in English.
Consider taking some Zoom 1-to-1 conversations lessons, but more for brushing up your knowledge and for peace of mind than for need. As said above, your English seems fine.