The same logic could very well work with fertilizer.
Making hydrogen via electrolysis requires 50 MWh per ton. Manufacturing ammonia requires tens of millions of tons of hydrogen every year.
BUT ammonia is a global commodity that can be and is distributed all over the world, so that means you can produce it wherever clean energy is cheapest. Chile has excellent wind AND excellent solar (best in the world), meaning you can operate electrolysis at higher capacity factor, and it has sea ports. So there are plans for big green ammonia projects being built there. https://renewablesnow.com/news/engie-enaex-plan-green-hydrog...
But it can also just provide food security by being a local source of fertilizer that is independent of global logistical constraints or fluctuations in availability of natural gas.
It’s also potentially an alternative mechanism for hydrogen storage. Some ships already run on ammonia, and you can run tractors (etc) on it as well without the extreme challenges in storage that compressed or liquid hydrogen have (its somewhere between LNG and propane when it comes to storage difficulty). However, it’s probably not a great consumer fuel due to toxicity.
Also, the US used to double electricity generation every decade. If something needs a bit more electricity, there’s no “scaling” argument why we can’t just produce more electricity. It costs money, of course, but there’s no part of it that isn’t “scalable.”
I also don't think you understand what it means to run an industrial plant at that scale or the logistics (pipelines and such) implied, particularly when the power source is so diffuse. You keep using the words "scalability" but it isn't clear you understand what that actually means in this context.
If you are interested in this stuff, perhaps you should study chemical engineering. The feasibility issues will be more intuitive.