You're right that it's theater, in the sense that the deal is already struck. But Zelensky's anger is real, because Trump's deal is---and always has been, since before the Russian invasion---the surrender of Ukraine to Vladimir Putin. Zelensky understands that he's going to be forced out of office and a Russian puppet will be installed in his place. He is understandably frustrated and angry, and is at least looking for ways to cost Trump as much as he can on the way out the door.
If you doubt any of this, then as you say, watch and learn.
To be fair, we have Japanese internment camps, slavery, the Trail of Tears, and several others. I'm not sure if this one is going to rank all that highly on the leaderboard.
I think many understand what is happening, but what can Americans do about it? Posting online and attended protests are not going to move the needle much. What I fear most is that violence might be the only solution, but I would love nothing more than to be wrong.
A general strike is the only non-violent solution. Of course people aren't likely to do that over Ukraine policy, but there are plenty of other things people are annoyed about domestically.
I do not see a general strike happening. It'd be great, but us cats are too fat right now. What I mean is that people are living too good on average. I think we are still in the 'crabs in a bucket' phase. So, I think if a general strike was organized, then many people would opt out because of selfish, albeit legitimate reasons, like not wanting to lose their source of income.
I am probably somewhat guilty myself, but I think a lot of people want someone or some group of people to take action on their behalf. Sadly, that is unlikely to happen.
Most Americans understand and oppose Trump's surrender deal. Unfortunately a significant number of them weren't paying much attention this past November and were conned into voting for the present predicament.
The EU has a substantially larger population than the USA, and for now at least, is adamantly opposed to the outcome you describe.
That might be what Trump and Putin want, but they are not the only interested parties here, and Trump is certainly succeeding at waking whatever beast-like qualities the EU/NATO may have left somewhat hidden in the recent past.
Unless the EU can substantially step up its military aid, that's the outcome they're going to get. There is one card that Zelensky and Europe could play, and that's European peacekeepers guaranteeing security. But that's boots-on-the-ground, and I'm not sure Europe has the stomach for that.
The body languages of Zelensky and Trump are fascinating to look at. You can clearly see that Zelensky is not playing. Also Marco Rubio, drowning more and more on his chair.
If you doubt any of this, then as you say, watch and learn.