Does anyone know of a program that can re-encode an mpeg2 PAL video into mpeg2 NTSC video without separating the audio and video streams
Even the best technique currently available for PAL-to-NTSC conversion (altering the pulldown flags) requires you to demux the AV streams. You cannot get around the fact that TWO aspects of the video must change: video resolution and frame rate. And of course, once you start talking about pitch-correction, you now have greater need to isolate the data for editing.
I don't mean to discourage you, but videohelp.com is a far better resource for this topic. Just type "Convert PAL to NTSC" in their search box (front page) and your journey will begin.