I think the primary problem with NTSC was more colour-related than lines-related, though the argument still basically stands.
Interestingly, this one went back and forth, AIUI. The initial British (monochrome) standards, which was very early, was quite flawed; later US standards improved on that, then NTSC improved on those, then PAL and SECAM improved on that (and bounced off each other a bit; the version of PAL that was eventually released used concepts from SECAM).
France, being France, did its own thing on the colour transition; SECAM wasn't used anywhere else in Western Europe (SECAM was better than both PAL and NTSC for the end user, but was hard to work with and not commonly used).
British and Irish TV channels, incidentally, continued to broadcast the pre-PAL standard on separate frequencies until surprisingly late. I believe the Irish broadcaster only stopped in the _90s_, when their conversion equipment became unreliable.
Similarly, the French first program ("première chaine de l'ORTF" before 1975, TF1 after) was transmitted in 625 lines SÉCAM on UHF band and simultaneously on 819 lines black & white on VHF.
Old black & white 819 lines was the more highly defined television system before HDTV.
Interestingly, this one went back and forth, AIUI. The initial British (monochrome) standards, which was very early, was quite flawed; later US standards improved on that, then NTSC improved on those, then PAL and SECAM improved on that (and bounced off each other a bit; the version of PAL that was eventually released used concepts from SECAM).
France, being France, did its own thing on the colour transition; SECAM wasn't used anywhere else in Western Europe (SECAM was better than both PAL and NTSC for the end user, but was hard to work with and not commonly used).
British and Irish TV channels, incidentally, continued to broadcast the pre-PAL standard on separate frequencies until surprisingly late. I believe the Irish broadcaster only stopped in the _90s_, when their conversion equipment became unreliable.