I'm not so sure of the history, but it's not so crazy that there are 'two' so long as roles are clear etc..
Nation states are funny things. They change slowly :)
One thing is for certain: there should be more control over who gets to be a 'cop' and the training and ultimate badge authority should be centralized at least at the state level.
This idea of 'Universities' hiring their own cops ... with authority to arrest ... who is in charge of them exactly?
I mean, in France they have 'two systems' but as far as I remember that covers everything and there are only 2 kinds of police uniforms that I ever saw. If there is one goofball cop/gendarme, his case will go pretty high up. Not to the 'dean' of the local college or whatever. Or to 'an elected guy' from some village.
In most, and perhaps all, states, there are state-level commissions to handle cases of problem cops. However, I will be the first to admit that they don't always work as intended.
The municipalities have, depending on the state they are in, forces they call police or "police office" but they are for code enforcement, public health and security, etc.
There is also a military police (Feldjäger) but they don't play a role in day to day life.
* The "Carabinieri", a branch of the military which historically which mostly works against normal crime
* The "Polizia di Stato", which became a fully civil force in 1981 and often compete with the Carabinieri
* The smaller "Guardia di Finanza", which is another militarized force but at the direct dependence of the Ministry of Economy, and deal with financial crime and smuggling
Until last year, we also had the State Forestry Corp which was its own corp and was, against many many resistances, absorbed into the Carabinieri.
They also seem to have a big chip on their shoulder when it comes to law breakers, they take everything personally and in their indignation often do the paperwork wrong. I have a few stories that are shocking, but to protect parties I won't recall them here.
I think the barriers to people with skills joining the force and enriching it with fresh blood are what is preserving it's holier-than-thou attitude to technology and the future while cementing their dumb and archaic process.
I think they could learn a lot from the PSNI, they've being around less than 20 years and seem to be a far more effective and modern organisation.
The bar was pretty low to enter the Gardai https://i.redd.it/fmlp8q1dwiiz.jpg
The US is particularly unique in that even amongst countries with relatively decentralised law enforcement, I can't think of another country where most major government departments have their own internal police force ("why is the Department of Education buying shotguns") or so many "primary" federal law enforcement agencies (FBI/DEA/ATF, etc) which would normally be much more consolidated.
+ normal police (immediate events such as car accidents, small burglars)
+ legal police (white-collar events such as economic crimes, bribes, traficking)
+ military police (acting as normal police on remote/wide field regions)
+ townhall police (events such as stadium security, car tickets)
+ secret police (mostly to identify society risks before they become problems)
+ military (in case of war/calamity they replace have precedence on all above)
This decentralization works OK. When the agents investigating a specific crime are suspected to be corrupt, at some point you see another agency taking forward the investigation and exposing the dirt. A recent case was the investigation about the criminal fires going in Portugal last summer. The military police was suspected of closing their eyes on the incident where +60 people died and the legal police took the case away from them.
The UK:
https://en.wikipedia.org/wiki/List_of_law_enforcement_agenci...
(I do think a lot of US police forces would benefit from a RUC -> PSNI style reconstruction)