It appears that some or all of these types of images are illegal in the US. The Supreme Court no longer holds this to be protected speech. From Wikipedia:
In response to Ashcroft v. Free Speech Coalition, Congress passed the PROTECT Act of 2003 (also dubbed the Amber Alert Law) and it was signed into law on April 30, 2003 by then president George W. Bush. The law enacted 18 U.S.C. § 1466A, which criminalizes material that has "a visual depiction of any kind, including a drawing, cartoon, sculpture or painting", that "depicts a minor engaging in sexually explicit conduct and is "obscene" or "depicts an image that is, or appears to be, of a minor engaging in ... sexual intercourse ... and lacks serious literary, artistic, political, or scientific value".
By its own terms, the law does not make all simulated child pornography illegal, only that found to be obscene or lacking in serious value. And mere possession of said images is not a violation of the law unless it can be proven that they were transmitted through a common carrier, such as the mail or the internet, or transported across state lines. There is also an affirmative defense made for possession of no more than two images with "reasonable steps to destroy" the images or reporting and turning over the images to law enforcement.
In Richmond, Virginia, on December 2005, Dwight Whorley was convicted under 18 U.S.C. 1466A for using a Virginia Employment Commission computer to receive "...obscene Japanese anime cartoons that graphically depicted prepubescent female children being forced to engage in genital-genital and oral-genital intercourse with adult males." He was also convicted of possessing child pornography involving real children. He was sentenced to 20 years in prison.
On December 18, 2008 the Fourth Circuit Court of Appeals affirmed the conviction. The court stated that "it is not a required element of any offense under this section that the minor depicted actually exists." Attorneys for Mr. Whorley have said that they will appeal to the Supreme Court. The request for rehearing was denied on June 15, 2009 and the petition for his case to be reviewed by the Supreme Court was denied on January 11, 2010.
In October 2010, a 33 year old Idaho man, Steven Kutzner, entered into a plea agreement concerning images of child characters from the American animated television show, The Simpsons engaged in sexual acts.[55][56] In January 2011, Kutzner was sentenced to serve 15 months in federal prison.
I hope that anyone who views this type of material or is thinking about it will take these facts into consideration. It doesn't seem worth having your life ruined over it.