The question is: do you infringe copyright if you share your screen while watching a copyrighted film with somebody else?
And the answer to that question is generally: yes, it's copyright infringement. Why? Let's see:
Are you infringing (Title 17 chapter 5, esp. section 501) on the rights of the copyright holder (Title 17 chapter 1 , esp. section 106) to distribute their film by making it available? Yes, you perform it, thus violating copyright. Especially notice these excerpts:
To “perform” a work means to recite, render, play, dance, or act it, either directly or by means of any device or process or, in the case of a motion picture or other audiovisual work, to show its images in any sequence or to make the sounds accompanying it audible.
To perform or display a work “publicly” means— [...]
(2) to transmit or otherwise communicate a performance or display of the work to a place specified by clause (1) or to the public, by means of any device or process, whether the members of the public capable of receiving the performance or display receive it in the same place or in separate places and at the same time or at different times.
To “transmit” a performance or display is to communicate it by any device or process whereby images or sounds are received beyond the place from which they are sent.
- Exclusive rights in copyrighted works
Subject to sections 107 through 122, the owner of copyright under this title has the exclusive rights to do and to authorize any of the following: [...]
(4) in the case of literary, musical, dramatic, and choreographic works, pantomimes, and motion pictures and other audiovisual works, to perform the copyrighted work publicly;
- Is a movie a work of art? Do you stream the whole movie? Are you usurping the market (people that have not yet seen the movie) from the movie distributor? Clearly, yes, yes, yes. This puts factors 2, 3, and 4 (nature is fictional, the amount is all, Effect on the market is that the stream is a replacement for a legitimate copy) against screen sharing on films. This makes it near impossible to claim fair use (Title 17 Section 107).
Case 3 is clearly illegal.
Case 2 likewise does not change a lot: being "internet friends" is generally not recognized, and would likely not stop people from being considered the public or a subset of it under the law - especially not if the group is large and could be described as "random people you met online". Under that pattern, even if a broadcast that is somewhat publically accessible (through word of mouth access sharing or something) would have not a single viewer, it would still be aimed at some subset of the public, which is the public. This in turn means, that even sharing with a single person that isn't specifically allowed to be shared with is illegal. However, it would be up to a court to draw a line between the is-Public of "these 42 random people Peter talks to on Zoom" and the not-Public which is "Peter, Paula, Maria and Marcus, who would meet and drink after work if not for COVID". However... Usage licenses apply, and streaming services generally ban re-streaming in their ToS (see below).
Case 1 has a Significant Other that might qualify as family under the law, and then it would not be copyright infringement. So it might be ok unless the ToS of the site make it a breach of the contract to re-stream to anyone. Which incidentally is banned in the Amazon Prime ToS. That would be a Breach of Contract claim of the streaming service against Victor, not Copyright Infringement.
But there is one difference: Copyright infringement needs to be filed for by the copyright holder. This means, the copyright holder needs to learn of the conduct first, then file suit with enough evidence. Which makes it incredibly hard for cases 1 and maybe 2.
However, it is still not technically legal if those people are not inside the "inner circle" that is not the public and there is the problem with the ToS, making it not ok even with that inner circle.