A few years ago I actually traveled all around the US and worked remotely with a 4g unlimited data sim card and was pretty amazed at the coverage, only very few places was I left without coverage. I'm guessing it's even better now?
You should spend more time out west or midwest in places like: Nevada, Arizona, Colorado, Montana, Wyoming, Utah, Idaho, Nebraska, Missouri, Oklahoma, Washington, North Dakota, or head up to Alaska, etc.
There are a lot of places in and around the Appalachian and Blue Ridge mountains that have no service.
Note: I know a lot of rural ISPs serving these markets, or that have been trying to for decades - I know precisely when StarLink will work like crap or be great for the customer (given options at all).
TBF that's like 70% of the US, large parts of the Southern Hemisphere in general, much of China, India, Russia, etc.
But yes, StarLink is best when it has some user density but not too much user density. It will be this way until... probably forever.
If I go camping? StarLink. Otherwise no cell/internet service.