In King of Tokyo, how does Mecha Blast interact with High Altitude Bombing?
If the card doesn't specify that the damage has to come from you it's not considered an "attack". The rules state 


  If a card deals damage when purchased (like Gas Refinery), this is not
  considered an attack. Monsters cannot yield Tokyo based on this
  damage, and cards that affect attacks do not affect these cards.


Since the Mecha Blast evolution does not specify that it effects an attack and since the rules also state that you can use your evolution cards at any time, then you should be able to add 2 damage to any damage that was dealt. In this case 5 damage would be dealt to everyone, including you.

Keep in mind that you must be alive at the end of your turn in order to win.