The real reason the US doesn’t use the metric system is that the US standardized their weights and measures separately from the French, and the benefit to metric is standardization, not decimalization. Jefferson thought that the international standard would be worth adopting (and was also a massive Oui-aboo) so he requested a Kilogram and Meter standard from the French, but English Privateers stole the first one and the second one (remember that they are made from precious metals) and the third one got melted down to pay the crew of the ship carrying it when they mutinied after being denied pay at while stopping at Bermuda on the way to the US.
By the time the 4th attempt was made, the US civil war was under way, there was better than a half century of inertia in the way, and a period isolationist (particularly anti-French) sentiment followed the civil war, so we just tweaked our standardized weights and measures a couple percent in order to refer to the SI standards and have carried on for another 160 years using both systems ever since.
It is important also to know that US customary is not the same as Imperial (the gallon is where this is most evident). The US standardized measures are based on the Winchester standards of the 16th century and US Costomary standards predate the Imperial standards which were adopted by the British Empire in the 19th century.