American customary units and imperial units both come from English units, so the US used various inconsistent English and other units in its early days. But the US never used “Imperial” units, which were not codified and put into effect in the British Empire until almost 50 years after the US had gained independence.
This map is apparently from Wikipedia, and is based on a 1995 CIA ethnolinguistic map. The version here is identified as from 2007, with some changes made by wikipedia commons editors (visible changes in Abkhazia and other places). The changes are marked as disputed and unsourced, and it does seem like someone took the letters marking general presence of an ethnolinguistic group (indicating sporadic presence) from the 1995 map and converted those letters into solid bands. This does seem to be a dubious change, as I cannot find any support for this solid separation of groups in Abkhazia and elsewhere.