The US has no issue with the metric system, and most engineering and scientific people switched decades ago. The military is mostly all metric too. The general public of the US is a harder nut to crack, asking a population of stubborn freedom lovers to change something they've known their whole life is damn near impossible.

I switch my stuff to metric all the time, and the usual response isn't "oh that's interesting", it's nearly always, "the fuck is wrong with you, why would you want that weird shit?!". If the government suddenly made all weather reports metric, the T-Shirt sellers would all become millionaires overnight from selling anti-metric slogans.

Americans use metric system for measuring bullets

I try to use metric as often as possible. I measure everything in millimeters in grams. I still haven't switched over to Celsius completely yet but I'd like to.

Haven't watched the video, but as someone who works in industry in the US I think the consumer side of a metric switch is the lowest barrier to entry. A much bigger hurdle is the fact that almost all of our raw industrial inputs are built on the imperial system. Need to buy raw plate or bar stock to have something built? It's sized in imperial. And if you want to source metric you're either going to have to pay more for it or look outside the US. And after that raw stock is purchased and you send it to a machine shop that machine shop is almost certainly using exclusively imperial tooling and measurement equipment. You can do the fake metric thing that some companies do where you dual dimension all of your drawings, but those companies will usually still design to imperial so their parts can be fabricated in the US.

I'm absolutely not opposed to a switch to metric. I still perform most of my calculations in metric and then convert to imperial just for ease and because that's how I was taught in school. But it's certainly much more difficult than just deciding one day that we're all going to switch.

heres my question. What do they use for a wood 2x4 in metric countries? And does the size actually match the name (unlike the US).

As I see it, the problem is that for the vast majority of people in the U.S. there is no compelling reason to change. People rarely need to convert units and rarely (but more often thanks to social media) need to talk to anyone who uses metric. I see it as a cultural quirk not unlike a dialect.

Of course for science, industry, and other situations where conversion, accuracy, and international communication are involved it very much matters and U.S. needs to use metric as much as possible.