Most public libraries don't have the resources to archive materials. That's mostly down to academic and specialist libraries, and the library of congress.
I’m in Illinois; under state law libraries exist as independent taxing bodies - the only way to underfund or otherwise interfere with them is at the ballot box, and it would take years of concerted effort by at least 60% of the local population (indicating that this is really what they want).
I have some family in Indiana; their libraries are funded and controlled at the county level to maximize what they can do cost-wise and to ensure that rural farmers also have access to all the resources. That structure also makes it much harder for goofballs to interfere.
That was the result of a specific deal Twitter made early on (itself a marketing stunt, of sorts). It doesn't mean the Library of Congress is generally in the business of archiving DRM-ed media on streaming services.
Also, the person above could have been talking about compared to days past. I can tell you the libraries I had access to when and where I grew are less funded (many closed), but again depends on where and what you’re comparing against.
The US is reportedly 62nd in the world in libraries per capita. [1] Given the US has more wealth per capita than most of the world as well, I think claiming we underfund our public library system is fairly obvious.
[1] https://onlinegrad.syracuse.edu/blog/best-countries-book-lov...
This is only the case if you think the proper level of funding is a function of population size or wealth instead of whatever is required to obtain sufficient results. If you're looking for results, it seems the proper level of funding would actually scale with population density (sparser areas require higher funding per capita to provide the same access).
I think you can make a case for that sort of model, but I don't think it's "fairly obvious".