What did people identify themselves with before nationalism?

Medieval italian cities would literally slaughter each other over buckets.

en.wikipedia.org/wiki/War_of_the_Bucket

Citizens of the Cosmopolis

self > family > religion > region

their family or clan
ethno-nationalism did exist to some extent but for the most part there was little to no identity outside of one's family beyond "you know what, I prefer doing business with people who speak my language."
There's also centuries of church propaganda which led to
Christianity vs Islam and Christianity vs other sects....but then again that only came up when differences occurred, not an actual identity.
this guy doesn't know what he's talking about. Large powerful cities with well-off citizenry would have pride (Romans) but for the most part noone cared about their country. Feudal territories would often switch hands without peasants, serfs, craftsmen, and even merchants really being effected. Again, there are exceptions but not much identity in general....people were uneducated and relatively isolated.

We don't know, since every civilization has evolved some form of nationalism with their cultural brothers before inventing writing.

Lower IQ [average was 75-80] in the early 20th century ad

People will stick to anything they can, they can fight for their nation, chief or favourite T-shirt colour.

Farm area > Social Class > Religion > Region

Family and God were enough

Pre-modern times were far more simple though - there wasn't much opportunity for a regular person to develop complex identities.

the patrician answer, everything is the modern identity ridden plebian projecting his taxonomy onto everything

It depends on what you mean by nationalism really. Some form of ethnic identity has pretty much been relevant for the entirety of history, but it obviously takes very different shapes depending on time and place. The meme of medieval people valuing religion over nationality has some truth to it but it's an oversimplification. In Bohemia for example laws divided Czechs and Germans the same way laws in Spain divided Muslims and Christians. Different nationalities were very real within the medieval mindset, but it had different implications than in recent history. A kingdom being multi-ethnic was considered potentially a good thing and national groups lobbied for separate treatment, not independence.

In the middle ages you can even find half-assed attempts at claiming lands based on their ethnic make up.

Country = King

In Ketts rebellion the common people proclaimed, despite in flagrant and open rebellion, "God save the King".
Their nationalism came from a vague idea of England and Englishness, which was centralised in a single King being.
Nationalism existed but only insofar as that people understood a basic loyalty to the state as representing their nation. They would be utterly confused if you asked, for example, should Wales be independent from England. The English did not care that Henry VII was Welsh or that he was a foreigner, once he was the sovereign that was the end of it.