Is Atlanta too far inland and too far above sea level to be affected by the comet in "Deep Impact"?
Tsunamis form as a series of moderate amplitude, long interval waves that travel away from the initial impact.  The first of these waves has the highest amplitude of the initial waves, and becomes the 'big one' later. Subsequent waves are caused by water rushing into the void created by the initial impact, bouncing off of each other, and starting the next wave out.  

As the radius of the impact waves increases, the power in each wave gets spread out over a larger and larger circumference, at a rate of $2πr$.  This is a steady geometric decrease in the power any given portion of the wave has.

As these waves start to reach shallow water, the waves in front begin to slow down.  This causes the waves behind them to become part of the tsunami.  This build up continues until you reach land.  Once at land, no more power is being introduced into the wave, no more water is being pulled in.  What you see is what you've got at this point.  None of the follow up waves will go anywhere near as far inland as this initial wave.

To elaborate, following landfall, the tsunami would encounter:


The barrier islands to Georgia's east protect it from most severe storms.  Their arrangement would also introduce an interference pattern into the wave that would incline the big tsunami to spread out more.
Beyond that, there is a large, flat area of low elevation where the wave would travel easily, but it would lose a large percentage of its power crossing this area.  Once again, the wave is losing power as it spreads.
Next, you get to the continental shelf that separates North Georgia from South Georgia.  In a rather sharp increase, land goes from a few hundred feet above sea level to, as you mentioned, 750+ feet.  That is one steep hill to climb for an old, tired tsunami.


Without subjecting this to a full simulation I can't be certain, but I think that any impact capable of creating a tsunami that could reach Atlanta would be completely unsurvivable.  Some of the simplest forms of life might make it, but everything else would be gone.

That does not mean that Atlanta wouldn't suffer substantial damage from other factors, such as all of the water launched into the air by the impact of a red hot flaming rock and any chunks of that comet that might break off from the friction of passing through the atmosphere, but right now Atlanta is pretty safe from tsunamis.