1. It would be very expensive to switch to the metric system in the United States (changing thermometers, speed signs etc.)
2. It would confuse a lot of Americans to suddenly switch to the metric system, since we are so used to measuring things in Fahrenheit and pounds it would be difficult to learn an entire new way of doing things in day-to-day life.
Sorry I couldn't think of anymore at the moment but I hope this helps a little!
