None of mine are bothered either, like Hannahs dogs they will happily sit and watch fireworks
My Vizzie was a small pup for his first 'firework season', so we took him out in the garden and played lots of fun games, and fed him yummy treats! I don't know if that is why he is not phased by them or it is because he is from pure working parents.
Lillie copied Isaac. Teva probably copied the other 2 - but her breeder played lots of 'noise' CD's to the pups, including the sounds of fireworks, so she just sat and watched, not even batting an eyelid