No. You don't understand. Ever.
Images of the under 18 in nude/sexually explicit poses/situations are always illegal, but the age of consent in 21 different states is either 17 or 18, including some of the "big deal" states - New York, Texas, Cali, Flo Rida. So if I was masturbating (i.e. engaging in sexual desire) over a girl under the age of consent then people from those states could accuse me of lusting after a "child."
I've missed you, I really have.