In all fairness, I think you have to consider the underlying basis of the cultural differences in each instance, and they're not the same. Hindus, while they don't, contrary to popular belief, consider cows to be sacred, do practice a form of militant vegetarianism that considers the cow to be a special symbol of docility and service to the public good, and which is rooted in Hinduism. Vigilante mobs in India have killed individuals who were suspected of killing a cow or eating its flesh.
Americans and most Westerners know dogs to be highly intelligent, loyal companions; our feelings about dogs are based, not on religion or even tradition, but on familiarity and personal experience. Hindus care deeply about the concept of the cow and what it means in the context of their society and religious practice, but they allow individual cows to wander around uncared for and sometimes starve to death. (In all fairness, some Americans are equally callous about stray dogs, but that attitude represents a small minority.) We value and care about the individual dog and its welfare, not the dog as a symbol.