> LA gov doesn't belong to CA gov, federalism, etc.

Federalism does not exist within states but between states and the federal government. Los Angeles (whether county or city) is an administrative subdivision of the State of California, not an separate sovereignty.

OTOH, Los Angeles isn't getting a .ca.gov domain because the state government doesn't want to dilute it's brand with local government websites, but that's about branding, not Federalism.

While it is true that federalism is a wrong term, but there exists a general idea of independence of different levels of government. I am not sure about US constitutional arrangement, but in country where i live there there is clear and explicit concept that municipal, province and country (executive) governments are independent of each other, not subordinate. Therefore, it would be inappropriate for city to get a subdomain managed by higher-level government entity.

The relationship between states and localities is governed by the constitution and laws of each individual state and not the US Constitution.

In my particular state, and in many but not all others, local governments whether that be counties, cities or towns are administrative districts which only have the rights and powers which the state chooses to delegate to them through state law and the particular charter granted by the state to the administrative district. The state through the normal legislative process can change those rights and powers or even eliminate a particular administrative district.

In the united states, municipalities are subordinate to the state (equivalent to province). They generally have charters outlining distinct areas of responsibility, but usually to change the scope of that responsibility requires legislation at the state level. At each level the executive, judicial and legislative branches are separate.