Monopolies aren't cartels. Cartels are where competitive organizations set parameters by which they choose not to compete.

Private insurance is cartelized, at least in many of the instances I work in. If an insurance company has a contract with a birth center within a 20-mile radius, they will not contract with another birth center. It does not matter to them that the 20-mile radius includes 8 miles of ocean. On the other hand, Medicaid is such that the price is the price and if your insurance company can make a profit at that price, you are invited to participate.

Veterinary hospitals are monopolistic. I'm unaware of any geographic cartelization.

Automobiles are the opposite of cartelized - a number of new providers (Rivian, Tesla, Lucid) are doing business and Tesla routinely drops their prices below profitability in order to protect marketshare from Ford and Chevy, for example.

Chicken is very much a monopoly. That's not a cartel. Groceries are getting there - but even then, Kroger is facing far more anti-trust red tape than they anticipated. Search is a defacto monopoly but that has a lot more to do with the monopolistic advertising practices of Google, which are currently under investigation.

I specifically said 'cable companies' and 'insurance' because they carve out geographic regions where they choose to not compete with each other for purposes of maintaining high profits. If you could only buy Teslas in California and only buy Lucids in Arizona the discussion would be worthwhile but as it is, there's about 40 brands to choose from in each state.