Thank you to everyone! I've seen the pics of CPUWIZ's NTSC Asterix NIB copy from 10 years ago with the "N" sticker on the top flap, and I've also noticed that the PAL boxes of both games have Four languages (i.e "English - One Player Only") on the front of the box, whereas the NTSC releases did not.
So, in regards to Asterix & Obelix carts, silver labels and '83 dates are both NTSC and PAL, while the '85's and '86's are PAL only. A small, square "p" label may be affixed to the back of the cart to signify PAL, but they easily fall off, so don't use that as a guide. Also, the "p" notation on the end-label indicates a PAL release.
I guess the only way to tell for sure that an Asterix cart is NTSC is to play it! I really appreciate this!