What is the non-European perception of Marie-Curie postdoctoral fellowships?
Speaking as a researcher in the USA, I would say that Marie Skłodowska-Curie Actions are clearly perceived as having significant prestige.
Even not knowing all of the details, one immediately sees:


It's an EU-wide program, and those generally have high competition.
Curie remains widely famous, and nations and organizations are protective of her name.


Exactly how prestigious it is compared to other prestigious fellowships I wouldn't care to speculate, but it's clearly a noteworthy addition to any researcher's CV.