Believe it or not, the US is not the world leader in cellular phones. We actually follow the rest of the world. Europe, in particular the UK, has the most competitive telecommunications market in the world. In this case, Europe is benefiting from greater competition than the US. They can call here cheaper than we can call into the next state. Calling to the US on an O2 Pay and Go plan can cost as little at 15 pence/minute (30 cents, but the math isn't as simple as that, you are better off thinking that the pound has the same buying power as the dollar). International texts are 10 pence each. Part of this is that their network deployment costs are dramatically lower than in the US, but part of it is also that landlines are VERY expensive in Europe (used to be controlled by the Post Office as a government service), they charge for local calls, and (very important, I think) the caller pays for all costs associated with a call. This is all the more confusing with the higher minute offers in Europe, since those minutes only apply to outgoing calls - not incoming ones.
They can call the US for cheap --- because American carriers don't price gouge international calls. Americans pay a lot of money on calls to Europe --- because Europe price gouging. This is why the CIA can monitor a bunch of Europe to Europe phone calls --- because they are all routed to the US and then back Europe for a round trip.
Mobile termination is ZERO in the US --- that's why Europeans can call the US for cheap.
European iphone plans have shown how uncompetitive they are when compared to the US.
Network deployment cost is cheaper in Europe because of higher population density.