Kinda? But also the law doesn't usually do anything to mere consumers. (TLDR at the end)
How severe the crackdown is from state to state is different, but all US states are pretty much "nah". Not because it's harmful to a real kid, but mostly due to obscenity laws
The likelihood of a regular shotacon getting in legal trouble for consuming and getting off to purely fictional characters is low.
From what I've seen, the child abuse hotlines will normally say "stop wasting our time" if you report an explicit sebaciel fic or doujin, because while technically illegal, they don't care.
When a shotacon or group DOES get arrested, its typically because they committed another crime (drug usage, piracy, etc) and the law tacks on the obscenity onto the charges for leverage.
TLDR: Technically illegal in the US, but rarely anyone is arrested JUST for reading or making the content, and usually have committed other crimes.
Also keep in mind i haven't deep dived into the law, and I'm just speaking about the US. I may be wrong on some details.ヾ(❀╹◡╹)ﾉ~
Iz ghis not extremely illegal