I live in a film landscape with very few writing teams. And do you know why Hollywood dominates the worldwide film industry? Because they can produce good scripts incredibly fast, and cheaply. The only reason most European things even get made at all is that these productions are subsidised by tax money. It makes no financial sense to compete with the oiled machine that is Hollywood, they simply cannot sustain the amount of good writers that the Hollywood system can. Writer's rooms with well paid writers are a huge upfront cost, but they are the reason that near everybody in the world watches Hollywood productions. Minirooms can't work as fast, or as well, and that's why they're creaming their pants about AI, because that can work even faster. If that output stops, they're going to lose so much foreign revenue. It's cheaper to program American content, but if there isn't enough of that, it's suddenly cheaper to program other foreign content. Who cares what language they're dubbing from amirite? Maybe domestic movies start to fare better! Right now, Hollywood attracts all the best foreign talent, too - Brits, Irishmen, Germans, Dutchmen, Italians, Swedish, French, Australian, South African, Latin American, Indian, Chinese - the reason they all get cast is not because it's more convenient for the Yanks to hire foreigners they often simply are world class greats. And they can and do work anywhere the work is good.
So no, the US couldn't put out so much good stuff with minirooms only. And if they already hold a lot of foreign chains hostage, saying so much capacity must go to their product - and goodness that's often what it is - if it gets too bad you cannot compel enough people to go see it even then. AI could resolve the unsustainability of minirooms by being faster, but it can't sustain a minimum of quality and that was already hurting the box office.
And sure one good writer can write a very good movie or series but they cannot do it fast, not for long, and even the best showrunners are already understaffed. If Hollywood cannot supply the cheapest "content" for movie theatres, Latin America, China, Africa and Europe are going to program any other foreign stuff, while India, New Zealand and Australia are going to buy other English language fare. Or perhaps they'll dub. Simply put you need a lot of writers and the very best actors to supply the whole world. Minirooms aren't cutting it, even the execs know that, that's why they're hoping to exploit people with theft machines.