Uh no, congress did not do that. Even if congress did do that you don't overturn a supreme court decision by writing another law. What congress did was more narrowly define what kind of child pornography is banned. It is now "such visual depiction is a computer image or computer-generated image that is, or appears virtually indistinguishable
from that of a minor engaging in sexually explicit conduct." So if someone developed a image metrics
child pornography, that might meet the standard of "virtually indistinguishable" and therefore be banned. A simple animation would not be.