It’s all based on the median household income. I feel like that isn’t the best representation if the median household is losing purchasing power over time due to wage stagnation, but it’s the definition they went with. From the article:

The report, which crunched the numbers for all 50 states, is based on Pew Research’s definition of middle class: two-thirds to double the median household income.

Just for some background information on how most countries tend to rely on larger, more rigorous regulatory bodies…

I am in the pharma industry (not in vaccines though). Typically the two main regulators that most other countries look to as a reference are either the FDA or the EMA (the EU organization). This usually means that if you can satisfy the requirements of one of these bodies, then it is satisfactory for the other country as well. However, it isn’t universal as each other country will usually have some modifications here and there for whatever reason. The most annoyingly particular ones I have dealt with in the past are China and Japan.

I work in pharma, regularly writing and filing things with the FDA (and other agencies), and this has been a topic of conversation at work. The good news for people is that the EMA is still a thing in the EU. So, at least the large pharma companies (like the one I work for), are likely to not really change much about their quality control/processes/etc. because we will still need to conform to the EMA guidelines which are typically in line with the current FDA (sometimes more strict, sometimes less so). The real quality concern would be smaller companies that only file for products in the US. They would only need to meet whatever new FDA guidelines come into effect (if they even do, changing stuff like GMP guidance is extremely complicated and time consuming) since the US is their only market.