I would be too scared of Google closing my account as retaliation for this and me losing literally my entire digital life (family photos, my identity that's tied to gmail, etc).
I could, and I probably should, but my time is worth something. For $25 I'd be doing it to make a point, but I'm not sure that point would actually be made.
This won't happen, because Congress has done its best to try to limit action against corporations by trying to define everything under the sun as 'frivolous lawsuits that are clogging up our courts'.
True. The demand letter you write prior to filing a lawsuit will usually be enough, though. At some point someone runs the calculation between giving you what you want and fighting a lawsuit in small claims, and decides to give you things instead.
A Chromecast retails for ~$25. Even if the presiding judge decided to award 100x in 'punitive' damages, that's still $2500, which is far less than what it would cost Google to bother addressing the claim in court.
You can sue Google in small claims court for the value of the undelivered Chromecast and for the court fees you spent on suing them.