I'm sure that might be true for some people who never make an attempt to assimilate - never listen to any English radio or go to English websites; don't have any friends outside of their own countrymen, etc. but some of that is a chicken and egg situation where they can't assimilate because they are afraid to come out of the shadows.
It's 100% BS for dreamers though.
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Late 40's Dreamer (Holy Fucking shit I'm almost 50 and still dealing with this), aged out of original DACA and didn't have a chance to apply for extended DACA after Republicans killed it on the vine.