There are some subtle differences between the US (actually North America) and the rest of the world. You have probably heard how people in the US pay for incoming calls, which is true.
In the North American Numbering Plan there are no area codes for cell phones as there are in the rest of the world. Consequently a caller doesn't know if they are calling a cell phone. In almost every country in the world, calls to cell phones cost more. In the US the recipient pays the difference. Elsewhere the caller pays the difference. In the US the recipient has bulk bargaining power so those calls are cheaper than elsewhere.
So if you really wanted to compare like with like, you should compare the cost of the US contract to the cost of what callers pay plus what you pay elsewhere. Note that callers can pay a lot more elsewhere - often 10 times as much as a call to a landline. See international phone cards to get an idea.
There are two other factors. One is psychological in that US consumers are very averse to variable billed amounts, and are prepared to pay more in order to have a fixed known bill. (I once read a paper I've never been able to find about this, showing it dated back to the earliest days of phone service in the US.) You may recall hearing how local phone calls are free. They aren't - you pay a higher base price. When I moved from the UK to the US my baseline phone service price quintupled. The difference is the local calls were "free" in the US while it was a few pence a minute in the UK.
The other factor is that there was no regulation requiring certain radio technology or interoperability. While the original GSM was good, it wasn't very future proof. It divided up frequency usage into time slots which meant you had a fixed number of possible calls. It also meant neighbouring towers couldn't use the same frequency. Qualcomm came up with CDMA which was very future proof - a phone talking to a tower sees all other phones (when they transmit) as background noise. Consequently it doesn't matter how the others talked to the tower so they could advance specifications. You could also put CDMA towers further apart than GSM towers. ("3G" etc are an evolution of CDMA all over the world.)
CDMA was adopted by two of the major carriers, but because almost no one else used CDMA that meant they had to source their own phones. That lead to a model where consumers got used to getting their phones from the carrier with no alternative. New phones were really cheap or free in return for a contract of a fixed monthly amount, which included around $20 per month just to pay the remainder of the cost of the phone.
Consumers are loathe to pay the real price of phones because they have never done so before. And carriers are loathe to have bring your own phone plans because the way their financial performance is measured is by ARPU - average revenue per user. Additionally because the carrier is bulk buying phones they can squeeze the suppliers, and they can "cripple" the phones to further their own interests. Verizon has been a master at the latter - for example they disabled bluetooth phonebook syncing several years back on a phone so they could push their own over the air backup service, they pull stunts with mapping (they have their own service) and even prevented Google's Wallet from working on the Galaxy Nexus (yup, they have their own too).
So like many things American we have this unwholly complicated mess where no one is paying the real price of anything, and what is actually going on is hidden behind other things.
If you are interested in how GSM and CDMA evolved, this is an excellent article http://denbeste.nu/cd_log_entries/2002/10/GSM3G.shtml