Final answer:
Noah Webster is primarily responsible for the spelling system of American English. He published dictionaries that established the American English spelling conventions.
Step-by-step explanation:
The individual primarily responsible for the spelling system of American English is Noah Webster. Noah Webster published his first dictionary, 'A Compendious Dictionary of the English Language', in 1806 and later, 'An American Dictionary of the English Language' in 1828, which significantly influenced American English spelling conventions.
Addressing the other questions provided for context: The Maya culture developed the first writing system in the Western Hemisphere. The most responsible person or group for the passage of the Fourteenth Amendment were the Radical Republicans during the Reconstruction era, not President Johnson. Alan Turing was the scientist mainly responsible for building the Enigma decoding machine, which was crucial in deciphering Nazi codes during World War II. Lastly, the invention of the radio is attributed to Guglielmo Marconi, who is recognized for his pioneering work on long-distance radio transmission.