>If anything, Appalachian are uniquely under-represented nationally. While the region as a whole contains nearly 25 million people, WV is the only state to have two Appalacian senators. I think TN has one as well, but, overall the political power of Appalachia does not at all seem sufficient to warrant extra attention.

Technically that is 50% more senators than California with twice the population.

Senators were just to make a comparison point against other rural areas (considering that the Senate is the place most rural places are over-represented). The same division though also ensures that, unlike Californians, Appalachians have relatively little voice in the electoral vote or for governor-level positions as well because WV is their only majority state.

A senator does you no good if your primary governmental irritant is the state government which for most rural areas is the case. The federal government generally doesn't do anything to egregious to rural areas (maybe because most federal policy mostly doesn't affect people's day to day lives or maybe because of those senators doing their jobs?) but the state governments generally have a problem with major cities enacting state level policy that should really be done on a county level.

Federally-funded farm subsidies are a huge deal to rural people in Midwest. Those are largely possible because mostly rural states like Kansas, Nebraska, Oklahoma, and the Dakotas have senators who strongly advocate for those deals.

Appalachians don't have the type of land that benefits from those subsidies, and they don't have enough clout to get an equivalent type of economic benefit package. The TVA was the last major economic project the feds funded, and it was hugely popular because it did actually improve the lives of people there. Better federal representation at the Senate level wouldn't solve every problem, but it could definitely alleviate some of the pain.

>but, overall the political power of Appalachia does not at all seem sufficient to warrant extra attention

They also serve (willingly or not) as exemplars held up by Republicans, particularly in the populist ideology of Trump supporters, of those "real Americans" who have been betrayed by globalism and progressivism, and to further the narrative of an intractable cultural and political divide having formed between the rural right and urban left (and to contrast the cultural and ethnic purity of the former against the corrupting influence of multiculturalism and secularism among the latter.)