As one who speaks both English and Spanish fluently, sometimes I notice small differences between both languages in terms of pronunciation.
One thing that has always caught my attention is that the "oo" sound in English (as in boot and moon) is pronounced with the lips rather unrounded. The Spanish "u" is definitely more rounded (and I think it's a little more fronted, too) and the difference between is, imo, strong. One of the markers of a Spanish accent in English is using the Spanish "u" to pronounce English words, which sounds weird and, well, Spanish. I actually recall reading an article once that stated that the "oo" sound is being pronounced more and more with unrounded lips in younger generations. I haven't noticed older generations sounding particularly different in this regard, but I do know that Californians definitely unround the "oo" sound way more than in other American accents. Such strong unrounding is one of the things that identifies
Now I've noticed that whenever the "oo" sound is represented in IPA, it's a [u], same as in Spanish. The two sounds are quite different to me and I've noticed that when U.S. Americans say words like "boot", their lips don't form an circle shape as they would in Spanish. There's definitely something different going on there, but I haven't seen it noted in IPA and I've never heard anyone or anything (besides that one article) mention this phenomenon.
My question is this: is the "oo" sound in English rounded or unrounded? Do you hear a difference between the "oo" sound in English and in other languages? Is it a generational thing? Does it happen in other dialects or accents?