That's only valid if you're comparing the US with 3rd World nations.
When mobile phones took of, even poor peripheral southern european nations (like mine) already had good fixed line telephone infrastructures and certainly the few people who didn't have a phone line yet weren't the kind that could afford early mobile phones.
In reality the fast growth in mobile phone adoption in the EU vs US is a case study in how top down enforced standardization can help markets: whilst the US had multiple network standards which required diferent phones and were incompatible with each other, in Europe governments were forcing mobile carriers (by making it a condition to get a radio spectrum license to operate as one) to use GSM, so all phones were compatible and pretty much from day 1 you could, for example, use your phone in a different country even though it was linked to a diferent carrier in your home-country.
Because of this, even though the mobile phone infrastructure started behind that of the US, it and mobile phone adoption grew much faster than in the fragmented US market and this was what allowed Nokia from Finland to, for a while, be the largest mobile phone manufacturer in the World (most of which they lost when smartphones became a thing).
Eventually the US itself ended up doing the same thing, if I remember it correctly by around the late 90s with v3 of GSM.