Say I had a Raid Bombardment. And I swung with a 1/1 creature, say Goblin Bushwhacker. Say I wait for the defender to declare blockers, and then use a pump spell, say Brute Force? Would Raid Bombardment still trigger? Or would Goblin Bushwhacker no longer fulfil the requirement for a less than 2 creature?
As long as your creature had a power 2 or less when it attacked it doesn't matter what happens to it after that.
From the Gatherer Rulings for Raid Bombardment:
The power of the attacking creature is checked only when the ability triggers. Once it triggers, Raid Bombardment will deal 1 damage to the defending player even if the creature’s power changes before the ability resolves.
Also, Raid Bombardment triggers during the Declare Attackers step, and will resolve before your opponent gets a chance to declare blockers.