Anyone seeing Moon on the 4th day (Chaturthi) of the Bhadrapada month would face blame and unjust criticism, its know to all Hindus but what about others across the earth.
The 12th Adhyaya of the 1st Khanda of Ganesha Purana(pg 83 to 88 in Hindi) gives a story of Ganesha's curse to Chandrama.
A brief summary of the story is as follows:
Once when all the gods are gathered around Brahma, Shiva Parvati were also there along with their two sons Kumara (Kartikeya) and Ganesha. Lord Shiva had a divine fruit which Ganesha and Kartikeya demanded together. Lord Shiva being confused asks Brahma for advice.
Brahma tells him to give it to Kumara as Kumara is older in age. Lord Shiva does so and then the family returns home. Brahma begins to perform creation. Ganesha is angry with Brahma's decision and he plants obstacles during Brahma's creation.
He finally appears before Brahma assuming a fierce form. Brahma trembles on seeing Ganesha's wrath. On seeing Brahma's fear at Ganesha's form Chandra laughs at him along with his attendants.
Ganesha is furious at this mockery and curses Chandra, "O fool, by mocking me thus you have shown your indecency, henceforth no one will see your face and those who do would reap sin."
This was problematic for the people on earth so the gods advise Chandra to propitiate Ganesha and ask for his forgiveness. Chandra does so and Ganesha modifies the curse to apply on only one day i.e. Bhadrapada Shukla Chaturthi.
The story is very clear on the curse affecting people regardless of if they know about it or if they don't know.
So yes even other people on earth who do not know about the story or curse would be affected by it.
Translation: On Shukla Chaturthi of Bhadrapada, knowing or unknowingly if one views the moon one is cursed with frequent/great sorrows, there is no doubt about this.