No, the county clerk records aren’t a “single source of truth”. In the US system, it is possible to convince a court the county records are wrong, and order them overridden-which makes them not the single source of truth.

By contrast, in the Torrens system, whatever the government records say are final. If you are the innocent victim of a mistake by the government (or a fraud against it), the government has to compensate you; but you don’t actually get the land back if it has since been sold to an innocent purchaser.

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.