Make sure your PAL footage is interpreted with the right Pixel aspect ratio.
A 720*576 file can be either D1/DV Pal or D1/DV Pal Widescreen
Create a new composition with the NTSC DV preset, again this can also be NSTC DV widescreen
Drop your footage in the comp and then use one of these keystrokes: Command-Alt-Shift-G -> this will make the video as high as the comp (there may be a few black pixels left & right)
or Command-Alt-Shift-H -> this will make the video as wide as the comp (a few pixels up and down are lost)
BTW: thats control, not command if you're on PC
There is also the issue of frame-rate, you're going from a 25 to 29.97 fps standard.
If you can get away with a slight-speedchange, I would interpret the footage as 24 fps, set the comp to 24 fps and then render using pulldown.
There are several other ways, try doing a search on NTSC PAL conversion