[Nagoyankee]

As a main islander, I have to say that it sounds like a different language all together. I've heard two natives talk to each other and I basically wasn't able to understand a word, except the few obvious proper nouns such as "Tokyo" or "Fukuoka", which shouldn't count.

I think it's important to treat the Ryukyu dialect and Ryukyu accent differently. While I don't understand the dialect at all, I pretty much understand the "standard Japanese" spoken by a Ryukyuan with a thick Ryukyu accent. When I hear the latter, I notice that many words are pronounced differently but it's still understandable.

As for your last question, it doesn't seem very scholarly to compare a Japanese dialect with an English one. I happen to have spent quite some time both in Kansai and Brooklyn in the past, but I fail to observe any analogy between the two. I seriously doubt that an Osakan feels particularly at home when watching a Woody Allen film.