Well considering he went to an English language school I doubt he didn't learn English or know it before going there. You are of course making excuses for a murderous Dictator who is happy to watch his country starve because of things that happened 70 years ago. He has access to the internet and Google translate, he has people around him who no doubt speak English, he is fully able to comprehend that America would have no interest in losing thousands of soldiers fighting a war in South East Asia against a country that wasn't trying to develop nuclear weapons.
One thing that is a bit of a wildcard though is how much living amongst that stuff has an impact - even with some exposure to the wider world living within that culture day to day probably causes some distortion - some people are more or less susceptible to it than others - look at religion where some people are completely convinced by some utterly crazy ideas despite having access to no shortage of material that objectively provides a counter-balance and others manage to interpret the same religion in more reasonable terms.