You can't have unlimited data plan in America in comparison to Europe because 1. America is much bigger and costly to operate as a mobile carrier than Europe.
2. Carriers have to recoup billions of dollars that invested early on in building its network
3. To make money, carriers need to charge $ somehow. They used to do that w/ voice plans (different tiers). For example, when the first iPhone came out, people actually cared about how many minutes they had in their monthly plan. That was the differentiating factor.
4. Due to the popularity of data based text app (WhatsApp, LINE, iMessage, etc.), people started to text a lot more (using data). Now, people also do voice talk via LINE, FaceTime, Skype, Google Hangout, etc.
5. Minute usage drastically decreased which led to voice-plan based revenue.
6. To survive carriers have to come up with a new pricing that profit from the new resource--data--that consumers love to use.
7. Compare American pricing and European is like saying how come European pay 2-3x higher in gas/petro than American do? There are many reasons behind our differences from government, policies, regulatory environment, geographies, to population densities, etc.
8. American carrier market is a free market with 4 big and dozens of small players. This is NOT an oligopoly but a relatively competitive and cut throat market. You can rest assured that the price you are paying is very close to a reasonable price that carriers must set in order to maintain an industry average profitability. This will happen by laws of economics as each company resembles a price taker because it's closer to a "perfectly competitive market" than oligopoly. I know you might argue that there are not that many players, but you have to understand that 4 plus all the regional and budget carriers are quite a lot of this industry. It's against law to collude or fix price and they increase their revenue largely from stealing each other customer. The series of uncarrier moves by TM that triggered these responses are a prime example of this market being a perfectly competitive market. In a perfectly competitive market, the price is NOT dictated by the sellers, but an equilibrium where supply/demands meet. It's a reasonable and most efficient price point.