I live on around 80 acres (30 hectares?). Our land is a bit unique in the area, and in general there hasn't been a single piece of land sold near us since before the pandemic and all the economic change that came with it. I don't know how the county could possibly know what our land is worth until something similar sells on the open market again.
Well, where I live (which is not in the USA) value-based land taxes go to the municipality and the school board. They pay for municipal services I benefit from: fire, police, EMTs, road maintenance, waste collection and processing, recreational facilities like a park, a library, and a swimming pool. Also schools, but that gets more complicated since some funding for education also comes from a higher level of government which collects income taxes.
Now mind, I live of 25 ha of swampland. But I get excellent value for my land-value-based land taxes.
In the 1970's a group of people decided to setup a micro nation on a small unclaimed island. A nearby country Tonga seeing they where not protected by another state invaded, so ended the micro nation.
Ultimately it's the US governments providing a military and police force that causes a piece of paper to have any impact on who controls a piece of land. Such services require payment. Though we charge for local services ie schools, EMS based with property taxes and protection FBI/Army based on people (income tax). Historically this favors land owners, but we could swap in the future.
Obviously we could lower defense spending but that's a separate question than simply the justification for taxes.
http://www.queenoftheisles.com/HTML/Republic%20of%20Minerva....
I don't think that's an easy assumption to make. Cost of living, average income, and average plot size are very different in rural areas. I don't know Idaho so I can't speak to land value there, but I can say farmable land in rural Alabama goes for between $1k and $6k per acre depending on the land. If you really want to farm it for anything more than a homestead, 40+ acres is a minimum IMO. On the high end that works out to $480/year, but with an average income in the area closer to $25k/year that number isn't insignificant when its a tax just for the right to continue to own land I already bought. Add to that the extreme challenge of even breaking even in farming today, I'd be impressed if anyone farming 40 acres in rural Alabama could reliably turn $25k in profit each year.
Related to that while we're at it, what is the government's justification for taxing the value of land I own outright? Are we classifying land and property ownership as a privilege rather than a right? And in a rural area where land isn't changing hands as frequently and farmland can often sit for sale for months or years, how does the government accurately assess value? In my own experience land value in rural areas is only really adjusted when new structures are built or a specific parcel changes hands, but maybe that is handled differently elsewhere.