In the Melting Pot decades people used to work hard to learn English and fit in. "I was born in ------- but now I am an American." Even with anti-immigrant fights and hiring discrimination against Irish, Chinese, Jews and each succeeding group.
Then, along with time wimpy corporations said to start "press 1 for Spanish, press 2 for English...." people became adamant that America would twist into a new shape for them. Eventually, Mosques would replace infidels' churches and synagogues. Children would be taught America was founded on slavery against blacks. American Western culture would be denigrated and then building and even park names, sports team names and holidays taken away.
When the Left realized that Identity Politics was the a means to get what they wanted and to create more victims, the melting pot you mention was destroyed and now everyone is special and deserves special treatment. For now, the Left and its different teammates still have a common enemy. Looking forward to when they don’t have that anymore and they start fighting among themselves.