Of course, English is also an incredibly difficult language for people to learn, and it's often considered (in the U.S., at least) very rude to compliment someone on how well they speak it... because such a compliment is often wrapped up with racism against non-natives and assumptions that if you're the "wrong" color, you must not be a native.
I don’t think it’s offensive to compliment a foreigner (to America) on how well they speak English…if you know when they started learning it, and it’s a wow You’re quick. It’s offensive to presume someone who is, for example, Hmong wasn’t born here and then compliment them on their English. Hint, if someone speaks English like they were born here, they probably were.
(I thought English is a relatively easy language to learn? The spelling can be tricky, yes, but the grammar is pretty straight forward. And even if a nonproficient speaker mangles a sentence, it's still usually easy to figure out the intended meaning.)
English is difficult because unlike many languages, it doesn’t have really have specific ordered rules, but instead a dizzying array of conventions, that function like rules. It’s a Kafkaesque bureaucracy of a language. Gaining the ability to communicate professionally seems ming boggling hard.
That said, because it’s more of a giant collection of words than a language, it’s always seemed to me pretty easy for a native speaker to understand what a non-native is getting at no matter how limited their English language skills are. Toss out a jumble of words you know, I can understand. So by that metric, it’s a pretty easy language to be able to communicate in at a basic level. It’s also not a tonal language, so when you pronounce things badly, meaning isn’t obscured.
I guess none of that actually helps anyone learn English, just saying that it seems like a language where doing it badly isn’t so bad. Half the people I work with don’t know the difference between “seen“ and “saw” ffs. But I know what they mean.
where it’s used, and America especially, is loaded with a-holes who won’t admit they know exactly what you mean. So there’s that problem. But not one of language.