While it is not a true "externality", data center use of water is a strong community/regional cost that effectively removes 1 person/1 vote. Those with the financial resources to buy more water get the water, those without do not.

Perhaps you think that the distribution of financial resources reflects what is in society's best interests - that Meta, Google et al. have demonstrated their utility in ways that make them literally more important than people with insufficient wealth to outbid those companies for water.

Many of us do not.