Also, Chinese script, even simplified Chinese, is significantly harder to master than English. I for example can speak Mandarin fluently (as a Chinese person in Canada) but can barely read or write it, and no you don't just "pick it up" if you can speak it because there is zero correlation between the spoken language and written script, it's all memorization of every single character. I would have to actually take classes or something to learn to read and write Chinese, which I am definitely considering doing.
Actually, English is technically my second language since I was born in China (long story, left as a young child so wasn't my choice), and after having learned English and become fluent in both reading and writing it, I keep asking myself "how the hell can you be fluent in speaking English and not be fluent in writing it? If you know how to say a word you know 90% of how to write it unlike Chinese."
So, sorry anglophones, even if China had the same literacy rate as the US, it would still be more impressive (not of the intellect of Chinese people or any racial bullshit like that, but the effectiveness of their education system and socialist ideology, which English speakers are fully capable of implementing as well with no excuse not to.)
I've been learning Mandarin for the past year and a half or so, it's definitely challenging. Learning to write in particular is incredibly challenging since learning to recognize the characters is an easier task than remembering all the strokes you have to make. My plan is to just use pinyin as input and just skip learning to write. English doesn't even begin to compare in terms of complexity.
Even I the anglophone am jealous of Cyrillic-script languages. Phonetic languages, where you say what you see, sound so convenient. Even worlds like anglophone have dumb gimmicks like 'ph' = 'f'. The grass is always greener on the other side.
But even then, illiteracy often also means they can't read basic English, so it's not even them misspelling weird words like..... 'misspelling' and 'weird.', a large proportion of the USA would seriously struggle to understand our conversation [see replies to this]. And when our alphabet is 26 symbols (52 including capitals) with 10 digits and a handful of necessary punctuation symbols, Chinese script is off by magnitudes.
And having seen some documentaries interviewing people in my country overcoming adult illiteracy, you realize this includes clearly intelligent people who within weeks could begin reciting their own small written speeches, who were often just neglected by the education system and then too embarrassed to seek help or reveal their inability.