I'm currently reading the Laundry series by Stross. The Laundry is a British secret agency that combats supernatural events and is concerned with a total invasion by extradimensional critters such as Cthulhu. Currently, they are in trouble as the UK Government has been taken over by an avatar of Nyarlathotep. The USA government is in a conflict as it is being fought over by those trying to awaken Cthulhu. Good books.
Anyway, my rumble is that this happens in various universes. Nyarlathotep takes over the UK government and Chtulhu almost has the the USA. This is discovered by the heroes of :
1. Potterverse
2. DC comic Universe
3. Marvel comic Universe
4. The movie variants of 2 and 3
What happens? In 3 - you can't bring in off Earth Cosmics to save the death. No Galactus arriving to fight with a deal with Reed. Places in touch with Earth - like Asgard (whatever it's current state is ) is ok.