Can you monitor any system in any country? Does the NTSC vs PAL matter?

Can you monitor any system in any country? Does the NTSC vs PAL matter?

The short answer is No, NTSC vs PAL is analog. 
The underlying issue though is presented in IP cameras, and fixed though another type of setting. 
 
There is a difference in the electrical systems in Europe vs North America, and this can cause lights to flicker and interfere with the image. This is compensated for by adjusting powerline frequency in the device GUI, you will often see options for 60Hz and 50hz is IP camera image settings.
 
If you have a camera that has strange artifacts and flickering near artificial light, adjusting this setting can resolve the frequency issue.