The same kind of penetration efficiency is in play when you’re trying to bootstrap a whole new infrastructure network like electric car charging stations.
US policy people were tied down to various abstract philosophical/economic ideas (and their refutations) which made comms, especially cellular services generally more expensive than other places. Coarse theory and such.
It's partly cyclical. Following the antitrust actions (Bell etc), the US had a great Telecom market. In the 90s, compared to almost any other country, US telecom service was amazing. Most other countries were highly ideological about "key industries" like telecommunications and it resulted in a mess.
In the cellular/broadband age, the situation reversed. Turkey is more of the "norm." US is the outlier.