The reason we don't give up the ghost over here can be summed up in one word. Construction! Every building, every plumbing fitting and fixture, every conduit of bulk cable, etc has been based on imperial measures for a couple hundred years. Nothing would work and nothing would fit together properly. It's one thing for say the auto mfg's to change tap sizes and use different bolts. It's another matter entirely when you're talking about 1000 sheets of drywall, $10,000.00 worth of kitchen and bathroom fixtures, reengineering roof trusses, stud spacing on walls, mating up with existing infrastructure, and the list goes on. That's just for one moderately sized house. Multiply that by maybe 100 million and include industrial/commercial buildings. Now figure in the amount of redundant stock all the contractors and retailers would need to carry. The costs would run into the trillions if not hundreds of trillions. With that kind of money on the line nobody is going to change a damn thing over here when we have a system that works fine as is. I guarantee if you owned a home in the states for 5 years you'd be cursing the metric system in no time flat!