That's all there is to it. The Japanese method is tens of thousands of people wanting to sell their art, and dozens of studios and distributors purely wanting to make money. Artists submit work and if someone thinks its good enough they give them a publishing contract. If they sell, they are offered more profitable contracts. That's it. It's like writing books anywhere.

Whatever is possessing the husk of American comics industry, it's not a functional business and hasn't been for a long time. Ostensibly it's two giant studios who are also the distributors. You can submit work to them or get a foot in the door through a connection inside and word of mouth. If they really think you got what it takes, maybe they'll give you a shot. "Got what it takes" means you agree with their company values and messaging, get along with the old staff, and are willing to work for peanuts. "Give you a shot" means you can apprentice under another artist for a while until you're ready, become a background illustrator, or if you're a writer they might even use your idea as the basis for a future Batman/Superman/Spiderman story!

It's not classic publishing model where they put anything in stores to see what gets an audience. They're just running on autopilot and the fumes of old IPs. Actual creative types tend to realize this early on and don't even apply. The people working for the industry are hacks who just want to make it big and get Hollywood to pick up their story for a blockbuster movie. The longer it doesn't happen, the more cynical and corrupt they become. This isn't even getting into the SJW parasites that infest and consume all rotten businesses now, who reanimate the corpse of their host to scream at you how it's not about the money - it's about sending a message.