The US government has been pretty good about cleaning up the UXO it knows about, which means what's left is the UXO it doesn't know about. You'll find it near most of the current and former testing ranges, particularly Yuma Proving Ground where there's trails leading right from the adjacent BLM land into areas with potential UXO. The only real barriers are a few signs and the law.

I see quarries everywhere, and they’re kind of required near any city or road project around Australia. Never considered them as a mine though… more like a ‘general resource site’?

Wouldn't that also filter out every open cut surface mine that strips overburden and directly extracts near surface coal, copper deposits, iron ore, etc.

Not every mine is a "classic" underground mine with tunnels, etc.

See (for example) the W.Australian SuperPit gold mine which consolidated every shaft mine in a particular region into a single open pit that goes deeper than any pre existing underground mine in that area.

Based on the info if you click into them, likely no. I would have expected them to be incidental materials from tunneling, but reading the description that's not the case.

Quarries?

The map has a "Status" predicate.

The US, like many countries and regions, has poor coverage of abandoned, closed, and shuttered mine sites despite such sites still posing an ongoing danger in terms of imminent physical danger (collapse, decay, etc) and untreated waste piles and ponds leaching toxins into ground waters, etc.

To answer the question posed, "how many (US?) mine sites pose a danger of type {X}" requires crawling the US BLM datasets, the OSHA datasets, the archived (from when active) MSHA datasets, and having a some luck onside for various specific sites due to large gaps and periods of not caring at all.

See:

* https://www.epa.gov/epcra/does-msha-have-jurisdiction-over-i...

* https://www.blm.gov/programs/aml-environmental-cleanup/aml

Various transnational global mining companies (Rio Tinto, et al) have extensive datasets on global resources and minesites, both operational, and past and potential future sites.