The willingness for people in the US to believe absurd lies about other countries correlates with its status as an official "enemy" or "ally" of the US government. Just like how the evidentiary standard around reporting on North Korea approaches zero. Americans will believe any absurd thing without evidence, and the media will shamelessly reprint official narratives, hearsay, and endless propaganda.
While the PCs used to program the PLCs were running XP, the 0-day that Stuxnet exploited affected all versions of Windows, at least from 2000 onwards, including 2008 and Vista.
EDIT: to clarify, the PCs "programmed" the PLCs indirectly, in that while they ran the Siemans STEP 7 IDE to design the centrifuges' control process, the resulting PLC programs were manually transported to the PLCs via USB devices, so there were two airgaps: the XP-running PCs airgapped from the outside world, and then another airgap between the PCs and the PLCs they programmed.
This massively trivialises how sophisticated stuxnet was, there were multiple 0-days affecting all versions of actively maintained versions of Windows being weaponised by the program.
It wasn’t a bunch of known vulnerabilities affecting unpatched machines. Quite the opposite.