I'd imagine if you weren't raised learning a language or around the language that it would be particularly difficult. I mean, I'm a born-and-raised bona fide Chicagoan, but I know Spanish like another language because I was taught that too by my Spanish mother.
Also, most languages, especially the Romantic ones, provide conventions(sentence structures, verb formulas) with irregularities and follow formulas while English is pretty dynamic and full of special situations, compared to most other languages, with tons of rules, not to mention homophones.
Homophones that even dick around with people whose first language is English.