>they tried to watch it in Mexico
Ask "they" if Mexico uses NTSC or PAL format
Mexico is listed as one of the NTSC countries.
So the question is not if Mexico is NTSC or PAL, but rather what settings you use to produce your burn to disc DVD.
The secondary question becomes, what did you produce
DVD-VIDEO standard or widescreen on DVD disc
AVCHD format on DVD disc
And, if you explore the contents of your DVD, do you find
OpenDVD Folder and VIDEO_TS Folder
Does what you produced play back on your own TV DVD Player? What did the viewer in Mexico use as the player for of what you sent?
The answers to the above should point to the troubleshooting strategy indicated.