Wiki - " The U.S. Metric Study recommended that the United States implement a carefully planned transition to the principal use of the metric system over a decade. Congress passed the Metric Conversion Act of 1975 "to coordinate and plan the increasing use of the metric system in the United States". The Act did not stipulate the conversion happen over a decade. Voluntary conversion was initiated, and the U.S. Metric Board (USMB) was established for planning, coordination, and public education. The public education component led to public awareness of the metric system, but the public response included resistance, apathy, and sometimes ridicule.[6] In 1981, the USMB reported to Congress that it lacked the clear Congressional mandate necessary to bring about national conversion. Because of this ineffectiveness and an effort of the Reagan administration to reduce federal spending, the USMB was disbanded in autumn of 1982. "

See we tried and it didnt take . The Brits switched over in the mid 1800's and we kept the old system .