I'm sure that (mostly the left) is going to spend millions of words going over things like why some people voted for Trump and how to reach out (the right doesn't give a damn about people that voted for Clinton, though to be fair, the politicians elected by the right don't actually give a damn about the people that voted for Trump either).
Democrats need to be better. This was true in the 90's, then the 00's and still in the 10's. The Democratic party just sucks. Obama is a cool guy who spent way too much time caught in the weeds negotiating with Republicans and trying to turn around people that hate him and what he stands for rather than fighting for the people who elected him (and, ironically, those who hate him too).
At that link the question is asked "Do we try to assimilate and emphasize our similarities, or do we celebrate differences and endorse multiculturalism?" and that strikes me as very wrong. That isn't an either/or proposition.
He is Jewish and says they assimilated, but there are lots of Jewish delis around (particularly in the northeast), Chanukah is--while neither a high holy day, nor largely celebrated--a widely acknowledged part of the winter holidays here and is commonly referenced in popular culture. Part of assimilation is celebrating differences and it is inherently an endorsement of multiculturalism. It isn't like Italians assimilated and now no one knows anything about Italian culture/food/history, because they are all just "American" now.
The catch is that in order for a new group to assimilate it has to be accepted by the broader community. This is almost certainly easier for people who look like the dominant [white Christian] culture. I suspect that this is why LGB (and even T) rights and acceptance have advanced so quickly this past decade while Middle-Eastern and Hispanic acceptance have been a bit slower, and even moved backwards. There's also a family effect where the stereotypical rural white man could end up with a gay son. He's probably not going to find out his son is Persian.