According to https://www.state.gov/foreign-language-training/ https://www.state.gov/foreign-language-training/ it's not very difficult, just tedious. They figur

According to https://www.state.gov/foreign-language-training/ https://www.state.gov/foreign-language-training/ it's not very difficult, just tedious. They figure mandarin or cantonese takes ~3x the number of classroom hours (2'200) that an easy language like french or spanish (750) would take.