Sure but if you happen to be in Hong Kong, which you can just fly into as an American with a standard passport, and you want to go to Real China and didn't both

Sure but if you happen to be in Hong Kong, which you can just fly into as an American with a standard passport, and you want to go to Real China and didn't bother with the Visa interview, then you actually can with this "one weird trick"! It's certainly a hard border, Shenzhen is as China as Tijuana is Mexico. So if you're in HK and have a day to travel around, give it a go, it's a fun adventure.