I kind of agree; it annoys me to meet people who emigrated and after years still speak with a thick accent and make strong grammar mistakes. I'm brazillian, and I observe this phenomenon both with foreign people in brazil (who apparently refuse to learn some vowels and gendered nouns) and brazillians who emigrate to english-speaking countries and still have crappy english.

I wonder why this is, though. First time I went to london (I was young) I was shocked that I, just out of movies and internet and some classes, spoke a better english than most working people I met in the streets who seemed to have emigrated there years ago.