I grew up with U.S. Std., and think that way.
Working as a motorcycle mechanic in the '70s, I became proficient with Metric.
Now, as a hobbyist, I prefer and choose to use U.S. Std. because it takes me back to the 'good 'ol days'.
But, working in Metric is not a problem, just requires a momentary schizophrenic mind flip.
Have also worked in B.S. Whitworth.
Takes a little longer, requires me to bang my head against the wall 'till I'm cross-eyed, then it works out fine.
I still have 3 barleycorns as a standard.
But furlongs take a fortnight.
Out here in ranch country, we buy 'bob-waar' in 80 rod rolls, and deal with bushels, cubic-yards, sections, shovelfulls, hands (horse height), and penny-nails.
My Japanese friends once asked me how large my home was, in 'mats'.
Huh??? Whut's a 'mat'.
Being dain-brammaged helps...