Perhaps. It is often said that neutered dogs become calmer and even often get a bit broader because they move less. This may or may not apply to all Chihuahuas. In the case of very sexually motivated male Chihuahuas, however, castration can often help to weaken the drive.
Neutering is never a solution for poorly behaved Chihuahuas. If your chi is aggressive or incompatible with other dogs, neutering will not magically eliminate these problems. Rather, the help of a dog school or a trainer should be used here.