To add a few things in, France and Russia were big supporters of SECAM back in the day, and so was a good portion of Africa.
And a good number of Asian countries used NTSC.
Also appears that larger South American countries were using PAL, and tiny European countries like Luxembourg and Andorra were using NTSC.
And another thing I would like to point out is that Japan originally used both standards; NTSC in the south, and PAL in the north.
It is interesting that there are so many TV video formats, and most countries pick PAL instead of NTSC. I never knew that there were Asian countries which used NTSC, and PAL and SECAM was so popular in Africa.