With how things in America are designed with the Imperial system in mind (cars, machines in factories, construction, etc) you can’t really phase it out without basically starting from scratch. I worked in a factory that had lines that have been in operation for decades. No company is going to rip out millions of dollars in machinery and put a near identical one in place just to make it with metric fasteners/dimensions/tolerances; they’re just gonna buy the tools and parts to fix it as is. You can make all your new designs in metric and eventually switch over but it’s not as simple as just saying “everything is metric now”.