Gerrymandering doesn’t directly affect presidential races, but it does affect them. States that were gerrymandered to Republican super majorities created rules to make voting harder for lots of democratic areas. They limited ballot access and purged voter roles in blue areas. It also affects the electoral college. As part of all the other tactics, it all made a difference.
Massive wars will break out over climate refugees invading the least affected areas. Billions will die and those left will be trying desperately to rebuild society. Nuclear contamination will be a real problem after nukes are used by middle East countries completely out of fresh water that Western countries are hoarding. Corporations will be outlawed after Nestle attempted to create a water monopoly and massive revolt saw their board murdered in public by a mob. Humanity will be 1/10th the population of today.