Has racism changed its primary justification over the past fifty years?Probably.
Is "cultural racism" a phenomenon worthy of concern?Honestly, I think "cultural racism" isn't racism at all. It is an offshoot answer to the question that is continually posed. Why aren't blacks (and hispanics, ect) successful to the extent the whites are today? If the only acceptable answer is 'racism', and any other answer is racist, then we aren't having an honest argument. Yes, racism is a often a factor but the answer is often also environment...the environment in which they grew up, social interaction, ect. The word used for that is usually "culture".
When an Asian child performs well by comparison to other children, they investigate and find that the Asian child's family makes him/her study 5 hours each day. Their culture values study like we value football. Ergo, this has an influence on performance and increases the likelihood of success. Do I want my child to study five hours per day? No, I'm willing to take the risk that they will not be as successful as Lee Ping so that they can enjoy being children. Not my culture...I'd like for them to be successful, but not at that cost.
Does the theory apply to the current tensions in the United States? In Europe? I don't know. Maybe.
Different example to make a point, but there are some tensions between North and South here. The culture of the South is slow. They don't value the same things the north does. I grew up around some people who
still call the northerners Yankees. They have a totally different view of what is important in life (speaking in generalities as I must because I'm speaking of a large group of individuals who are obviously not identical). I'm from the south, but I've spent so much time in the North it takes me a while to get used to the way things are done down south when I visit my family. And in parts like the Mississippi things are REALLY slow. Go to a drivethrough and expect to wait a while. Call the theatre and expect an actual person to answer the phone with 'hello' , rather than a recorded customer service message. The conversation will go something like this. Him/her: "Hello" (silence); You: "Um, yes, is this the cinema?"; Him/her: "Yep" (more silence); You: "I was wondering, um, what is playing today"; Him/her:"Well (long pause). Let me see (long pause) We've got Underdog (Underdog is drawn out at lenghth over several needless syllables, as though he's trying to find the next entry on one of 30 separate post-its and doesn't wish to pause between movie choices), and the Simpsons." You:"is that all?" (L-O-N-G) pause "Yep. Have a nice day."
The above isn't the way things are done in the north. If someone asked why southerners underperform northerners (and they GENERALLY do), well, what is there to say other than culture? Black northerners are more successful (well, score higher on IQ tests) than white southerners in general. That doesn't mean that every southerner is destined to be unsuccessful or ignorant, but it would be dishonest to pretend that the culture has absolutely nothing to do with any of it.
Edited to add: I'll continue (why not, since I've already muddied the water?). A personal anecdote: Take my father-in-law, born in Cuba. He is brilliant. He has an IQ measured at over 160. He is also unbelieveably lazy in many respects. If he has a job, he'll work 48 hours without rest, but he would also sleep 48 uninterupted hours. He has come up with about 15 inventions that he created simply to make work easier (he's an electrician, plumber, carpenter, cop, realtor, pilot, engineer, computer programer, ect...). But he has never bothered to patent any of them. Some of his inventions have actually been stolen by visitors, and they got rich off of them! He just shrugs and says, "Oh, well...too busy, no point in patenting anything because it's too much aggravation."

I'll tell you, those inventions were never stolen by any Latino visitors that frequent his home, but by ambitious white guys who ask, "So...how does this work? uh, huh..." He wrote an entire computer program with 500 page manual, was only about three days away from finishing it and never bothered to finish it.

and his family is EXACTLY the same way. ANd my husband? The same. Brilliant but not ambitious at all. He is successful, he works hard, but he'd never in a million years step over anyone to succeed....and he'd as soon not work at all if it wasn't necessary. And when everyone else is pinging off the walls with stress, he's cool as can be. I swear, that man could nap while under seige.