No system is really better than the other. But the metric system is waaay easier to figure out. The problem isn't with the system, but with the American public and the fossils that work in government. You have senators and congressmen there that have been in their job for 20+ years and are set in their ways. Why are we the only country to use the imperial system?? Because Americans, on the whole, fear change. I think it's funny how cars sold in the US have both KmPH and MPH on their speedometers, but if you go to our friends in the north, their cars only have KmPH.
The big problem I think you would see if the US changed to the metric system would be at the gas pumps. The criminals that run big oil who charge you $2.10+ for a gallon of gas would just change it to $2.10+ for a LITER. It takes more than 3 liters to make a gallon.
Other than that, you would also have to figure in the infrastructure changes virtually every manufacturer, other than soft drink producers, would have to make. It doesn't seem like much, but the dairy farmers would have to change their machines to liters, not gallons, oil companies would have to change their quart bottles of oil to liters, it doesn't seem like that big of a problem until you look at the machinery costs. I can pretty much guarantee you that if someone in congress introduced a bill to convert the US to metric, every lobbyist in the country would start paying off politicians for the big manufacturing companies because in the end, buying politicians is cheaper than buying new machines.
This kind of thinking applies to a lot of things that are wrong with this country. Why don't we have a lot of alternative fuel vehicles on the road? Because big oil pays the politicians to keep it off the senate floor. Could you imagine what would happen to oil profits if the government mandated all new vehicles attain a minimum EPA rating of 40MPG and use nothing but synthetic lubricants? That alone would hurt oil companies in a big way. Never mind if the government said that the cars also had to run on something other than petroleum based products. Imagine a country of hydrogen powered cars, getting an equivalent of 40mpg using all synthetic lubricants. Oil companies would lose billions and eventually most would go under. Sure, there will always be gasoline powered cars in the world, but the numbers would diminish greatly when the people driving them start getting charged $8 a gallon for gas and up.
It's just the way this country operates. The government doesn't run the country, the huge corporations that make more money than the government can print do.