2. I don't even understand how a title transfer could happen without verifying ownership. Is the title system in the USA decentralized or that much different than elsewhere? i.e. Torrens-style
The claim that the title insurance industry is the reason for lack of adoption of Torrens title schemes is uncited, and immediately followed by descriptions of several cases where Torrens title was adopted (often poorly) and later abandoned.
Fascinating, how is ownership established if there is no single source of truth?
I feel the answer to this is also crucial to understanding OP. It could be a minor annoyance or the real possibility to lose your land.
There is: the county clerk in the county where the land is located.
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.
First, it doesn't seem like that's always the case, based on another post upthread talking about a land ownership case that went to the high court because of an error in the government's records.
Second, since there is no single government for the entire world, any government trying to implement a Torrens system is still going to face the problem of events happening outside its jurisdiction that its records do not and cannot contain, which affect ownership of property in its jurisdiction. So there cannot be a "single source of truth" in the sense you appear to be using the term, even in the Torrens system.
Excuse my German ignorance, but my understanding of how it works here is that unless the transfer is notarized, logged and recorded with the local authority, there has not been a legal transfer. So, by that definition of land ownership, no "events outside of its jurisdiction" can take place. Any such agreements become binding only upon their verified registration. A notary is responsible not only for confirming the transfer but also as independent consultant so neither party gets seriously ripped off. (And if they didn't, they would be in serious liability trouble.)
The "share of the database" is managed and owned by the local government, but its records are available all across Germany for authorities to look up. The vector database of lots is public, and there are procedures to request access to ownership documents for various purposes. The procedure is that when you want to buy a certain property, the owner confirms that you have permission to get the official record directly from the land registry, which then become the basis for any serious negotiations as what is recorded there is in fact the single source of truth.