Most regular homeowners insurance coverage will not cover vermin damage, which includes snakes if they believe that it was a maintenance problem that you could have prevented. If there was a way to stop the snake from getting in the unit, then they would reject your claim because you knew that you had snakes in your area, but did not bother to take the necessary precautions to vermin proof your ac unit.
There may be some exclusions such as if the snake bit into a coil or broke something inside of the unit that would eventually stop it from running aside from the noise, then that might be covered. You would have to really look at your policy and check out the fine print of what is written about vermin. In some cases, it may depend on what state you live in as to whether you can get that exception of coverage. If the insurance does not cover it and you have an extended warranty, check that out to see if your warranty would cover the damage. Homeowners insurance can be fickle about covering a lot of things and vermin is definitely one of them. The best way to find out if they do is to give your insurance carrier a call and explain the situation to see what they say about it.
In some cases, you may get a specific rider policy aside from your regular insurance that might cover vermin damage. If you get a rider that covers snakes getting into the unit to do damage, then you can make a claim to have someone come out and fix your unit. Depending on where you live in the United States, there are rider policies like this one that would exist because of the area in which you live.