I wanted to know if my little boy Mitch (a male American short-haired) will stop growing now that he is roughly around 1.5 to 2 years old and weighs around 17 lbs (might be overfed a little) and he has been neutered.
In general, cats stop growing when they are one year old; this means your cat will not get longer or taller, and the growth stop is gradual, not a sudden stop.
In this article on pets.thenest.com you could find more information about growth of cats.
A cat will continue to develop for another year until it looks like an adult cat, but the changes are relative small.
I am a little concerned about the weight of your cat; a two year old cat is normally not overweight due to the normal playfulness at this age and the energy used when it plays.
Here is the article about American short-haired cats on cattime.com that contains some more information.
You need to give the cat a food formulated for spayed/neutered cats, establish fixed feeding times and do not feed more than the instruction on the package says.
You have to stop giving treats to your cat, or at least only give treats once a week, and do not feed your cat foodscraps at all.
I am not saying you do any of this, so please see this as a general advice.
And last: play more with your cat and keep him active more of the time, maybe give him more/other toys. Cats like variation when they play, so they do not get bored.