Many Italians started dropping vowels as soon as they arrived in America.
They couldn’t afford to keep them.
The southern regions were occupied by Spain for a long time, beginning sometime in the nineteenth century. Since it was the dominant culture at the time, the people copied the Spanish way of saying the Italian words, many of which had close equivalents in Spanish.
The people were so much more isolated than they are today, in villages, so every area developed its own dialect.
This was definitely not something that started her in the U.S. I remember when people came from Italy, they spoke the same way.
There is also the word lu for il (the) in Calabrian Italian dialects.