is drawing actual underaged children performing sex acts a crime?

No, the SCOTUS itself has ruled it is not unless its indistinguishable from a photo of the child, such as pasting their head on a nude body or is "reasonable to be believed" that it actually was them. Might fall under defamation though. Its in fact been protected as free speech multiple times.

Point being, the king of "Drawing lolishit" didn't get caught with anything so the reasoning of "all lolicons are also into CP" has a major chunk against it. Regardless of how gross they are, they aren't criminals by default.