You're trying to say that because they did it and they're poorer it should be easier for us because we're richer. First of all, the cost will be in proportion to the activity of the economy and the population. Second, the proportion of people who were educated to use units of any kind was a smaller proportion of that smaller population. And in many former-non-metric countries many quantities are still often quoted in the old units.
All of that and it is still the case that the primary system in the US is the metric system de jure if not de facto. De facto, the metric system is virtually universal in science domains in the US.
Whether the metric system is "better" or not is not the question. There are keyboard layouts not actually designed to slow down typing, but it's just one of those things that most people don't see worth changing. Are they wrong? In that case, it's an individual valuation. I'm sure "the US economy is losing $500b because of QWERTY" would make great copy on a slow news day on reddit. But unless it costs Not everyone is a relentless optimizer. Even some of us who are also like to optimize for the entire system, including transaction costs/overhead/maintenance and not just some ab initio declaration of right like god in genesis.
The US has a great solution that everyone hates because it's the US: we use metric where it's necessary and leave it alone everywhere else. We could use a lot more European know how in numerous other sectors. I would even go so far as to say it's probably correct to presume that things where the US is the outlier is a case where we are the ones doing it wrong.
It's a presumption, meaning evidence can rebut it. In this case, here we can manage both. We can teach both in schools, we can use computers and calculators to divide by numbers other than 10 (which you have to do with mixed units and constants in metric calculations anyway). In fact, I wonder if there's proof that all of this extra teaching and double system overhead is worth what it costs! I bet the answer is that it is though and as long as you can experiment and find out in your domain, it sounds great to me. Different systems for the win!