I live in the USA and I am going to Mexico for vacation. From what I can tell from my research, mexico does not have a max altitude limit for drones. So my question is when I go to Mexico is the Mavic software going to give me any trouble when I try flying over 400 feet inorder to record some mountain ranges.

you can change the max altitude in the app.  (even when you are in the US)
It will make you accept responsibility, but it will allow you to change the upper altitude limit

Will that void  DJI care if I do accept ?

Sure you can fly over 400 feet. This is the high between aircraft and ground. If you fly up to a hill over 400 feet high you must fly over 400 feet at the end to avoid crash to ground.
If you want to fly over 400 feet Above Ground. You need to ensure it’s legal to do so. Most important is safe to do or not. Are you sure there is no aircraft or helicopters flying low around there?

You can fly as high as you want but beaware of the area you do and note that is not legal

max alt AGL is 1650 feet or about 500m      so 1650 feet/500m AGL from wherever you take off from  that firmware/software limit.

AGL = Above Ground Level
will dji refuse warrenty/care service.  no very unlikely since laws and functionality arent interconnected

laws/policies we have in the US and most countries is 400 feet AGL max.  but you can certainly fly well above that if you desire, however you maybe in breach of laws and policies so use caution and know whats above and around you if you decide to do so for whatever reason.   i sometimes fly above 400 feet AGL, but i do that only if i know the airspace and airtraffic..  if i dont i dont fly that high, i usually skim fee feet over tops or trees or 275 feet AGL to compensate for rising ground/floor

Manned aircraft level starts at 150 meters and can be even lower for e.g. rescue or police helicopters. That should explain why we should never fly higher than 100 - 120 meters and always in VLOS.

In my area, crop dusters fly very low to the ground for obvious reasons.  More than once I have suspended my flying activity to avoid any interfearance with the pilots' flight pattern.  I leave nothing  to chance.  Safety First.

400' above the ground. Though up to 500m above the home point - providing the drone remains max 400' above the ground at all times during the flight

It would depend on the policy of the location and the environment as well I strongly advise do not fly your aircraft in hazardous areas.