Are we talking about a different country than the USA? There's ~174 million potential voters in the US, 77 million voted republican vs 75 million voted democrat at the last presidential election (https://www.statista.com/statistics/1139763/number-votes-cas...)
So there's an about even population split that is in theory in support of those policies, versus the same amount of people against. Surely it's not "one state against what the rest of the country voted for" like you're suggesting...
No. That's not it at all. While Federal law is the supreme law of the land, it is enforced by the Federal government.
The several states and any municipalities within them are under no obligation to enforce Federal laws, just as the Federal government is under no obligation to enforce state and local laws.
Which is why the Federal government often ties funding to legislation, using the carrot of funding (and the stick of pulling such funding if states do not) to compel states to cooperate with the Federal government.
What's more, the Federal courts (including SCOTUS) have repeatedly ruled that the states are not required to enforce Federal law for the Federal government.
And no one is "unilaterally deciding to override the immigration policies of the federal government." In fact, state and local law enforcement have repeatedly been used to back up Federal agents executing those immigration policies.
No Federal law requires a state to enforce Federal immigration policies. And not enforcing a law outside of a law enforcement agency's jurisdiction (again Federal law is the jurisdiction of Federal government not state/local governments) isn't "overriding" anything.
You appear to be confused about the law and how it works in the US and the several states. Here are a few links to help straighten you out:
https://www.cato.org/commentary/yes-states-can-nullify-some-...
https://supreme.justia.com/cases/federal/us/521/898/
https://supreme.justia.com/cases/federal/us/505/144/
https://www.lawfaremedia.org/article/can-the-u.s.-government...
Be careful with this argument. Cops also don't have any "obligation" to stop crime, so if we take this argument to its logical conclusion, then it's fine (or at least, it's "not unilaterally overriding laws") for a cop to stand by while someone gets lynched.
You're just figuring that out now? You're 50 years late[0] for Warren v. District of Columbia (rape, assault and burglary) and 20 years late[1] for Castle Rock v. Gonzales (triple murder).
Maybe you should start paying attention?
[0] https://en.wikipedia.org/wiki/Warren_v._District_of_Columbia
[1] https://en.wikipedia.org/wiki/Town_of_Castle_Rock_v._Gonzale...
Personally I'm not sure I have a huge problem with this, yes it's a mess, but I'm not at all convinced we need more consolidation of power just because of that. I'm DEFINITELY not convinced that one side or the other has what it takes to permanently govern everything and always get their way.
The same general principles are at work when it comes to the legalization of weed, with lots of little details being different of course.