Can you get pay as you go sim cards in the US? They're pretty common here in Italy and are a decent way of not getting too deeply involved with the carriers.
The US carriers seem to market PAYG plans toward low-income customers who (in the carriers' eyes) would not be able to pay for monthly post-paid service plans. Thus they bundle the plans with cheap feature-low phones.
The carriers also don't allow smartphones to be activated on PAYG plans, instead requiring you to buy into an expensive (and profitable, for the carrier) data package.
This is crazy.
The thing that totally sucks in the US market is the lack of PAYG data plans, or for that matter the price of contract plans for data only. They 3x the price of Europe.
Plus, it's a little different that Europe. When I've been overseas in various European contries, they get free incoming calls. My wife would call from the States using Skype for a couple cents a minute and it wouldn't cost me a dime. Here in the US, it's an awkward system. You pay for all your minutes[1] and most the large carriers (Verizon, AT&T, etc) even charge daily access fees, up to $1/day whether you use the phone or not[2].
[1] Unless you get one of those hybrid plans, where you are pre-paid/off contract, but you pay for a certain number of minutes per month. [2] All the carriers differ, some only charge on the days you use the phone. T-mobile seems to be the best "large" operator for pre-paid service in the US, though there are decent regional MVNOs with good deals.