A surge protector for an AC split unit powered by a Siemens EQ Loadcenter
Surge protectors come in a wide variety of form-factors, and you don't even need to protect your whole house, you can protect particular circuits.  That is decided by where you place the protector. 

The problem with "surge protectors in a circuit-breaker form factor" is that breakers do not interchange across brands.  You cannot put Brand X breaker in Brand Y panel, unless Brand X has specifically built that breaker for Brand Y panels and UL has tested and classified it for that use.  

So you are probably better off using a "goes in a knockout" type suppressor.  This will let you use anyone's brand and a common $10 breaker, instead of paying a big premium for one specifically for your panel.  You can install this anywhere - it can go on its very own 2-pole breaker, where it'll protect the whole house.  Or you can install it out at the air conditioner shutoff switch (if it's wet rated).  

If  you install it at the air conditioner, it will better protect the air conditioner (and the house from the air conditioner's own spikes) and less well protect the rest of the house from external spikes.  

That's because long wire runs tend to weaken spikes also. By putting the spike suppressor at the air conditioner, the suppressor spends less of its bandwidth/capacity fighting surges that wouldn't make it to the A/C anyway, and 100% of its capacity on ones likely to affect the A/C. 

Internal spikes are a thing. You can have one of your appliances damaging another, and large motor-driven appliances are a major culprit. Putting the spike suppressor near the air conditioner means it will "catch" any spikes from the A/C unit before they get near the rest of the house.  It will also do a better job protecting A/C electronics from A/C motor spikes! 

However a suppressor at the A/C unit will do a lesser job of protecting your computer from external power spikes, obviously, since the long cable run will dampen its ability to neutralize those spikes. 

Nothing says you can't install as many surge suppressors as you please, so you can fit 1 at the A/C unit and 1 in the main panel.