USA NATIONAL DEBT QUESTION!!!!!!!!!!!!!!!!!!!!!!!!!?

Why can't America just print of its national debt? I understand inflation and all that crap and devalue of the dollar, but consider if the notes are printed out and NOT introduced into the economy. Hence your salary stays the same hence no inflation. Basically the notes are printed out and sent straight away. Now you may argue that since more has been printed out, whether or not introduced into the economy, now each dollar is worth less, and there is more, BUT what happens if its done secretively? Hence no other foreign countries would realize that now there is no extra bills, hence no higher costs???????????????????????