When I first read your comment I wanted to say that managing with these units isn’t really all that difficult. But, then I remembered that I have a magnet on my fridge that converts teaspoons to cups to quarts etc. I don’t know anyone who keeps that info in memory. Doubling or halving an American recipe can be an exciting math project
It’s fun to see what metric conversions an American has memorized. If a person can quickly convert miles to Kilometers, they are probably a runner. If you ask a group of colleagues how many grams are in an ounce, the dude who quickly say “28.3 give or take” is a pothead.