[quotemsg=18907015,0,2367627]I don't get what's so hard about doing what almost every other country already does, and prohibit using the phone while driving.[/quotemsg]Because the US is so unlike most other countries but most people don't understand that, especially foreigners.
First, consider the US Constitution. While many countries have charters and documents modeled after it, very few explicitly limit the national government in the way the US Constitution does. In particular, the First and Fourth Amendments are taken very seriously. Anything that prevents someone from being able to express themselves how they wish or that tampers with their personal privacy and security send up an immediate red flag to most Americans. It's just a common trait most have this side of the pond.
Second, consider the size. The continental United States is as big as all the European countries combined ( minus western Russia ). Texas alone is bigger than any western European country. My home state of Utah is twice the size of England and is half the size of France. Me going to southern Utah or Vegas is farther than going from London to Paris. Some co-workers were coming to Salt Lake from Mumbai. They said they wanted to visit Chicago on the weekend, thinking it was a short train ride. It's 1400 miles ( 2250 km ) away. That's the same distance as Dhaka to Mumbai, or Berlin to Madrid.
Next, population and population density. The US has roughly half the population as Europe ( again, excluding Russia ). And half the US population is concentrated in 5% of the land. Meaning that's lots and lots of open road all over the US. How far does the average American commute to work? Average Brit? Frenchie? Spaniard? German? How viable is public transportation? Hint: it's really easy to get reliable and usable mass transit in small, highly populated cites. It's a lot harder when you have hundreds of thousands of people spread out over hundreds of square miles, like anywhere between Missouri and Nevada, North Dakota and Texas.
So, how do you plan to enforce this? It's easy to pass a law. It's a lot harder to enforce it, and most people either forget or don't know that. Yes, phone manufacturers could make their products disable themselves if they detect they're going faster than 5 mph. How is it supposed to detect if you're the driver or passenger? How does it determine if you're in a cab or on a train? How many people would buy those devices? How many would hack the system and work around it? How would the phone report abuse? How would that reporting system be secured against intrusion and abuse?
In short, when someone asks "why can't this work there where it works here?" the usual answer is "Because 'there' works very differently than 'here' and you don't know all the variables."
However, the US already has numerous laws against driving while distracted. It's up to the various executive branches to find ways to enforce laws ( or modify them if they're unenforceable ), not kick it down the road for others to do their job.