Complaints about systems of measurement is the topic every Internet forum should prohibit in their rules, but none does. It's strange. Politics is tame in comparison!
A foot is the distance light in a vacuum travels in 1.01 nanoseconds. A meter is the distance light travels in 3.33 nanoseconds. It is not really a big deal what you name that, they are both totally arbitrary. They have no relationship to any core feature of the Universe except by some reverse-engineered arbitrary constant. (You start by defining that there are 9192631770 transitions between the two hyperfine ground states of caesium-133 atoms in a second. You then build the meter by saying that light in a vacuum travels 299792458 meters in 1 second. There is no special meaning to 9192631770 or 299792458; they are totally made-up bullshit constants that mean nothing. Kilograms are even worse; before 2019 it was just a big arbitrary ball of metal in a museum. I won't even mention how the base unit has the prefix "kilo". How crazy someone is for not using the elegant kilogram/meter/second unit system. It's just so pure and natural!)
It seems pointless to me to argue over (or worse, get high-and-mighty over) what these constants are called. SI has a bunch of bullshit constants. The imperial system has a bunch of bullshit constants. It's bullshit all the way down, my friend. As long as you know what constants to use, which is why we name units, then it doesn't really matter which you use. None is better than the other.
Arguments about units usually devolve into how crazy it is that people use fractions with imperial units. But nobody using the units for real things uses fractions; for low precision applications, sure, people will say "a half inch", but when precision matters, it's "500 thou". And people use fractions with meters/kilograms/seconds, they say "half a second" when they really mean "500ms" or "500.000000000ms" or whatever. (This is all weird to me because fractions exist in real life -- you can fold a sheet of paper into thirds. But there is no way to express it in a decimal dimension. You can make three sections that are 33mm, 33mm, and 34mm, but that's not quite right. So I guess you make them 33.33333333333mm, 33.33333333333mm, and 33.33333333334mm?)
It gets weirder when you start using the SI prefixes. There are names for every power of ten, but people only use certain prefixes with certain base units. Nobody ever talks about centiamps, but they'll happily use centimeters. Nobody ever uses deci-anythings, but there it is on the trivia test for SI prefixes. And of course, computer people thought that prefixes would be pretty useful, but we make bytes from 8 bits and not 10, so a kilobyte is 1024 bytes... for some reason. (It's 8192 bits, of course!) Decades later someone decided this was stupid and invented new words for every SI prefix just for computer people. The best case is that you sneak in an extra letter for every quantity ("1KiB") and people will think you made a typo and interpret it as 1024 bytes... exactly as they would if you wrote "1KB". If you want to refer to 1000 bytes you ... just say 1000 bytes because there is no byte prefix that means 1000 unambiguously. (The only people smart enough to benefit from this were marketers. They could write 1K and say "well we thought you were using SI prefixes" and convince customers that they were getting 1KiB of storage for the price of 1000 bytes. If it sounds too good to be true it probably is.)
So this all continues to be arbitrary. What about fastener sizes? The metric system gave us the intuitive ISO metric screw thread. How big is an M4 screw? The minor diameter is 3.242mm, which is obvious from the name. An M4 socket head cap screw accepts a 3mm wrench. An M10 screw accepts an... 9... erm... 8mm wrench. (The SAE/UTS system makes even less sense, if that's possible. It's wire gauges and threads per inch, I think.)
Anyway, my point is that it's all super arbitrary and to do anything you need a lookup table. You can go look at a cesium atom and you'll have no idea how that defines the meter, kilogram, second, or inch without a lookup table. You'll never be able to make a screw with just one number ("M4"). So it's not really worth making snide comments about.
To answer your actual question, why does the US use the metric system? Because we started doing science and engineering before the metric system was invented. There was no reason to switch because there are no benefits in switching. It's all arbitrary.