It seems that London and the Home Counties have some go-to lazy stereotypes for The West Country, Wales, The Midlands, East Anglia, The North, and so on. And they for each other and of course for London and the South. It's less a city/country thing as region/region. Or does it come more from city-dwellers in the regions? Maybe so.
Obviously some city-dwellers disdain slow-witted 'Country Bumpkins' and 'Hicks from the Sticks', the world over, I imagine. And vice-versa for 'City Slickers'
How well-meant or bantzy this all is depends. Sometimes there's real venom and prejudice but it can be so boring, unoriginal and predictable however benignly meant.
Getting back to Wales. It's short of cities or even that many sizeable towns. You can scarcely feel living in rural Carmarthenshire that you are condescended to by people from LLanelli or Swansea. Let alone Carmarthen. As for Pembrokeshire people feeling inferior to people from its only city! (because St Davids has a cathedral so its nominally a city though smaller than most small towns and large villages). Plenty of historic counties have next to no decent sized towns.
Unless I'm mistaken Cardiff would be the only domestic candidate and I never get the impression that Cardiffians feel especially metropolitan to be fair. People from Wales's other nearby cities like Brum and L'pool perhaps more so? Or am I prejudiced?
Then there are of course those silly things like 'They only speak Welsh when they don't want to be understood' but you hear that from all sorts of people, Welsh included.