I.E. Are US ISPs, particularly big ones like Comcast, required to geolocate ISPs to the state where the person is actually in? What about mobile ones?
Where I live (not US), it is extremely common to get an IP that Maxmind geolocates to a region far from where you actually live.
I run a geolocation service, and over the years we've seen more and more ISPs providing official geofeeds. The majority of medium-large ISPs in the US now provide a geofeed, for example. But there's still an ongoing problem in geofeeds being up-to-date, and users being assigned to a correct 'pool' etc.
Mobile IPs are similar but are still certainly the most difficult (relative lack of geofeeds or other accurate data across providers)
This is mostly because of how APNs / G-GNS / P-GW systems work. E.G. you may have an APN that puts you straight in a corporate network, and the mobile network needs you to keep using that APN when roaming. This is why your roaming IP is usually in the country you're from, not the one you're currently in.
I've heard of local breakout being possible, but never actually seen it in practice.