>>212323268"Strange worlds" as in spooky dimensions, hell, and sometimes space.
And aside from the 30 second montage of falling through other universes, the movie really just had one alternate universe and didn't fully exploit the concept it's named for.
There also wasn't much "madness". Wanda was going berserk but internally its somewhat justified from her perspective and its not like her motives are incomprehensibly insane or anything.
It could've functioned exactly the same way if had been a time travel movie, or a movie that didn't have any kind of alternate timeline shit, America was just a girl from Spanish Harlem or whatever who develops super powers, and everything happened in the "regular" world.