The other part, the segregated ethnic lanes is often referred to as "patchwork quilt". The idea is there is no assimilation only people living side by side in harmony, but we're seeing exactly how those borders between identities are creating mayhem, not harmony.
Patriotism is liking your country and wanting other people to become part of it if they want to. After all, if your country and culture is the best then people should be allowed to become part of your culture and thereby become better!
Nationalism is liking your country and wanting other people to be kept separate. After all, if your country and culture is the best then anyone else is inferior and shouldn't be allowed to dilute your perfection!
The theory might not be correct
Bulworth: "Everybody just gotta keep fuckin' everybody 'til they're all the same color".
From the movie "Bulworth":
I've been thinking about this a bit lately and it reminds me of the "melting pot" metaphors we learned about in middle school. Rather than having a bunch of disparate, competing identities I think America is only going to work well when we form a single united, composite identity. I'm not sure if this is nationalism or not, but if it is, it's an ethnically-inclusive nationalism which seems markedly better than the scary kinds of nationalism from the 20th century and earlier. It probably does imply some assimilation, but it's not necessarily everyone assimilating to some "white identity"; rather, everyone assimilates toward the composite "American" identity (whatever that is). I'm not sure if this is what "multicultural" refers to or if it refers to the more progressive ideal of segregated ethnic lanes competing with one another, but the last 5-10 years makes me feel like the latter is untenable.