But almost all countries are more liberal than those two. My question isn't if the US and UK are the least enlightened countries in the world, but rather, if people see them as particularly enlightened among countries. Ie compared to any other random liberal country like Mexico or Czech Republic.

I understand OP's point, just curious whether the examples used reflect a common perception. To me when thinking of stereotypically enlightened societies, I think of Iceland or Canada or something. The US I think of more as a business+war society, and UK seems somewhere in the middle, but much lower than the rest of Europe.

This is based on nothing objective, just wondering what other people's perceptions of these places are

I understood "enlightened" to mean "espousing modern values of enlightenment" - basically fostering a belief in science and reason and trying to push mankind further in terms of technological and moral progress.

In this regard, both of those countries would be considered B-tier at worst.

This is my perception as well. Not knocking either of those countries, just curious if they were thought to be bastions of enlightenment values.