How much cost difference is there between backpacking one continent vs another?

I am interested in taking a 2-3 month backpacking trip this summer. I intend to live frugally and buy only essentials, but money will still be a factor.

Are certain continents much more expensive to backpack than others? For example, how much cost variance is there between Africa, South America, and Europe?

I’m an American, in case the USD conversion to the different currencies makes a significant difference.

Any information or comparisons are much appreciated! Thanks!