Aw GEEZUZ Jordan! You gotta think about things 'fore you open your mouth. The only place for the energy to move the ran drop can come from is the bullet. No ifs. No ands. No buts. If the bullet gives up the energy to move the drop, the bulloet is effected. If the bullet does not move the drop it is unaffected.
If you've ever shot in the rain or very humid air you will see a sizable "tube" of disturbed water along the bullet's path. The perturbation of all that water and the change of state you see is energy given up by the bullet.
Your physics is flawed. Quit arguing with everybody
The bullet transfers energy to the air around it WHETHER OR NOT IT IS RAINING. It's called drag, air resistance, or fluid resistance. Take your pick.
Ever heard of a "sunk cost" in the business world? The energy lost to creating that pressure wave ahead of the bullet, aka air resistance, is a sunk cost. A rain drop that is moved out of the way by the air molecules is moved by work done by the air, not directly by the bullet.
Another analogy to try and help you visualize this: If a jet fighter is approaching a wall (much like a bullet approaching a rain drop), and the jet fires a missile at the wall (like the bullet pushing the air ahead of it toward the rain drop), the jet loses some energy by pushing the missile, but the impact between the missile and the wall does not exert a force on the jet at all. The jet sails right through where the wall used to be (assuming it doesn't get hit by any debris). Likewise, the bullet sails right through the space where the drop used to be after the air wave pushes the drop out of the way, which air has already absorbed some energy from the bullet, drop or no drop.
