The proverbial Melting Pot where all immigrants assimilated into one American society is no longer applicable. When other big immigration groups came into this country a few generations ago the situation was very different from what it is today. Many early immigrants made the hard decision to come to America with an understanding that they were breaking ties with their old country. Learning a new culture and a new language was not a choice. Our society was a true melting pot and immigrants were expected to fully assimilate into the American culture- but things have changed. Today the term Salad Bowl is often used as a substitute for the Melting Pot. In a salad you may have different ingredients tossed together to form a perfect combination; but the ingredients maintain their differences and do not blend into the mix.
Assimilation no longer works because our society is different now from what it was before. New immigrants today can easily maintain close ties with their home country through Internet connections, telephone communication, and accessible travel. They are also able to have access to their cultural heritage and language through product and service offerings that are targeted to the Latino community. The idea of diversity and maintaining one's heritage has become very important in the American culture and works against the assimilation tendency.
For more information see the post “U.S. Hispanics need to learn to speak English!” Says who? in the Latino Opinion blog.