And most important, all words ending in "a" need to be pronounced as ending in "er".
Examples - Dali Lamer, Barack Obamer.
That's not actually how it works.
Correct English goes like this: you drop the "r" at the end of a word which possesses one unless it precedes a vowel. So "I have a daughta" but "I have a daughter and a son." The "r" is conjured into existence by the "a" in "and".
Incorrect English also drops the "r" at the ends of words that have one unless it precedes a vowel; but it also adds an "r" at the end of words that don't merit it because of not having an r in them when they end with a short unstressed vowel sound and when they precede a vowel, as though they were words like "daughter". So someone who says "I like Obama" would say "I like Obamar and Biden"; someone who says "The Dali Lama lives in Tibet" would say "The Dali Lamar is Tibetan"; Samantha makes me hot" but "Samanthar is a babe".
But no-one just slaps on an "r" willy-nilly; if it happens at all it only happens before a vowel. If you listen to someone speaking incorrect English they will still drop more Rs that you think should be there than they will add Rs that you think shouldn't.
Now, is there some sort of connection between how Bostonians drop the "r" at the end of words while the English add "r" ant the end of words. In Boston, "bomber" would be "bomba" (Richie Valens must have been from Boston) while the English would sing "La Bamba" as "La Bamber".
Yes. The Bostonians are speaking correct English. So are some of the English, as I have pointed out. All English people would say "bomba" unless it preceded a vowel, and no English person, however depraved, would actually sing "La Bamber" unless "Bamba" preceded a vowel.