But at least in some places in the US that's actually just a log of some kinds of transactions (sales and mortgages): you don't have a normalized field in a database somewhere that spits out "this person owns this spot" instead you have to build up from each individual transaction- plus there are transactions that don't take place on the log, e.g. deaths and inheritance or marriage/divorce that could take place outside the purview of the county clerk.

e.g. a married couple buys a house, then one of them dies, and the will is recorded in a different state and leaves their property to their kids rather than the spouse, that sort of update would not be recorded in the county clerk's office in my state.