perhaps the brand of camera/nvr would be useful information to share...
but typically no, with digital it makes little difference.. I am running a mixed american/china/european setup right now and everything works fine.. I kinda like PAL as the substreams have a bit better resolution than the NTSC ones.. even watching cars driving by on the roads I cant see any difference from 25 and 30fps, so 25fps max for pal/euro seems like a fair trade.
my PAL NVR works fine on my NTSC tv, and my NTSC cameras work fine on my PAL NVR..
if you were working with analouge signals, completely different story.. those are actually formatted/encoded differently, whereas digital is exactly the same formatting/encoding with different settings.