Yes, I am Chinese by ancestry and birth. Came to the US at age 4. Because I spoke Shanghainese in the family my Mandarin is heavily American accented but my Shanghainese is good. As for the other branches of Wu, I am able to understand them well. To me, they sound like heavily accented versions of Shanghainese. My father's family is from Suzhou and my mother's family is from Ningpo. It is very interesting that the Shanghai regional dialect is called Wu because I know so many individuals with families from the area with the last name of Wu, my mother's side of the family included, I believe the Mandarin spelling of Wu is Hu.
There are many Mandarin names with the same sound Wu as well. My sister-in-law's maiden last name was Wu in Mandarin but in Cantonese it would be spelled Ng (in Chinese it is the one you add a "man" on the left hand side to character "five"). The one with Mandarin Hu (Hu Jiantao's last name) would be pronounced Woo in Cantonese (film director John Woo is one).