In my experience, Americans actually do work reasonably well with some kinds of metric units, but temperature is a notable blind spot.
It's been hot lately, and thanks to climate change, it hasn't just been hot here in California (where a 40C/100F summer heatwave was never uncommon)--places like England are getting crazy heatwaves too. This has led to a lot of discussions about temperature, and because these conversations are happening in Internet chat spaces where people come from many different countries, there's usually one round per conversation of people having to translate their numbers between Farenheit and Celsius, usually with a bit of snark about how weird and backwards Americans are for using the former.
It got me thinking that we never have to have these translation pauses for other metric units that come up sometimes, and I'd say the reason for that is that Americans actually get exposure to meters and liters on a regular basis, but temperature gets left out.
If you buy a ruler in the United States, it will usually come with inches marked on one edge, and centimeters on the other. A nice foot-long ruler has 12 inches on one edge, and 30 centimeters taking almost the same distance on the other, and you'll see both every time you use the ruler. So we're exposed to the two on a regular basis, and know that the length of a standard ruler is "about 30 cm" the same way we know that it's 12 inches.
Anyone who participates in long-distance sports gets exposed to kilometers; even in America, races are often specified in kilometers. Anyone who has run or walked a "5k" event knows how far that feels, so many of us have at least that in our muscle memory too. (A notable exception is the special status of 100-mile "century" events; a "century" always means 100 miles, that unless we specify it is a "metric century"--in which case we might just call it a "100k".)
Liters are also not too hard to deal with. In the United States, milk is sold in gallons (and fractions thereof), but soda is sold in liters; anyone buying for a crowd will get the very iconic "2-liter bottle". So, again, we have a good everyday frame of reference for how much a liter is; it's half a big soda bottle.
Temperature, however, lacks an everyday reference point.
Sure, we use SI units whenever we're doing any serious science, but that's not the same context as walking outside and feeling how hot it is. One can buy thermometers marked with both scales, but I haven't used one of these in a long time, because so many temperature displays today are just a number. It's not like milk and soda, where each scale has a place where it gets used that everyone can get familiar with. The only time anyone in America specifies temperature in Celsius is when they need to make sure an international audience can follow along, or when they want to push people towards using it on principle.
In the absence of such examples, anyone who wants to learn to "think in Celsius" has to make a conscious effort to do it, usually by cutting off access to data in Farenheit...and that's not unlike teaching oneself to use a DVORAK keyboard. Why bother if you don't have to, if you're already so used to the possibly-flawed-but-good-enough alternative (which you probably will be, by the time you're old enough to realize there might be a problem)?
An effort to move the US to metric stalled and died in the 1970s, and frankly, if you want to actually improve people's real quality of life, there are better ways to spend your political capital. Pills cost too much per pill regardless of whether they're measured in grams or ounces, houses don't get any cheaper if you measure their lots in hectares, and the number of people killed by the police each year is just a much-too-high integer: no units required.
So until someone can figure out how to package temperature like soda, giving Celsius its own easily-accessible place to shine, we're going to have to keep translating for each other.