Ethnicity isn't the only thing you have to worry about. I suspect you'll see a lot of "anarchists" playing in this mix. Certain leftist groups are definitely prepared, and they've been funded for decades.
Travis McGee wrote a really interesting (and viable) essay, and I think the reason he didn't include that (among other things) is because of time and space constraints. There are only so many facets and aspects one can introduce into a concept without starting to take away from it. However I agree with you completely that ethnicity is not the only issue, and in my opinion will not be the main issue once things really start moving (please note: I'm black - but not African American - thus I may be biased).
My reasoning is as follows. While the beginning stages of a societal breakdown will definitely be quite stark in terms of ethnic based strife (especially since rioters and looters will be from minority groups), and the scenario so clearly illustrated by Travis McGee will play out more or less as shown (ie rioters comprised of mostly urban youth cleaning out supermarkets, then attacking targets perceived as vulnerable, leading to the rise of countermovements - mostly White male - to stop the thievery and killing of the urban mobs). Also, as shown by Travis McGee, the countermovements can be very effective due to the superior tactics and weapons used (on aggregate).
However, very soon new dynamics will come into play. The US is a country of over 300 million people, and while minority populations are a part of that the nation as a whole is bigger than just 'minority urban youth.' The MUY mobs will be quickly defeated (and probably more so by hunger sapping their strength and will, making then to collapse inwards, than by lone wolves at the back of trucks). The big problem is that the rest of the country - the nonrioting placid law abiding citizenry - will also start going hungry. Need medicines. Water. They may take longer to break than the urban minority youth, but break they will.
Look at your average suburbian 'estate.' Many houses in close proximity to each other, absolutely no food or water storage (since there is always clean piped water and WalMart is only a 15 minute drive away), and total reliance on the system for everything (you name it - for security, medical care, everything). The average suburban home is just a more affluent version of a Section 8 home ...they all suck on the government teat, with the main difference being that in the ghetto it is more overt and by far more basic. But both average examples of each suckle hard and long off Uncle Sam.
When the system crashes most of suburbia, after spending the first week fending off the zombie like urban mobs moving from the inner cities into suburbia, will start to turn into zombies themselves. By the start of week two most homes will be out of food. At first they will rely on friends and neighbors who were better prepared, but by the start of week three even those neighbors will stop being as 'generous' once they realize things are not getting better as quickly as they thought they would. People can be very generous when they think they are in a short timeframe sh!t storm, but when there is no end in sight people start to hoard. That's when the fabric that was holding things together starts to shear and shunt. If a kid is sick and hungry a person will ask their neighbor nicely, and if told no will go home. Same thing day 2,3 and maybe 4. After a business week of a crying hungry and sick child, and the belief that the neighbor is 'unfairly' hoarding supplies, things quickly change.
In my (probably wrong) estimation, suburbia will be a huge killing zone. Not because of rioting black youth in the first week or two, but rather by the MUCH LARGER unprepared suburban population that is totally desperate and cognitively disparate. The minority urban youths will not last a week, but the average suburban home is surrounded by dozens upon dozens of homes (not to mention the hundreds more in neighbouring suburban estates arranged in close proximity), and most of those homes have people with absolutely ZERO preparation. At most they have one of those water cooler bottles, and maybe enough food for a week or two.
When the system collapses these people will band together to protect themselves from the first wave of 'zombies' - the inner city you. However, if things are not back to normal by the end of week two it is these same people who will become the second (much larger) pool of 'zombies.' A much more dangerous threat.
Now, the above applies to even Conservatives (even FReepers) who live in suburban areas with no preparation. A hungry child and a nagging spouse asking why there hasn't been any food and little water for 10 days doesn't care if you supported Gingrich or the Ayatollah. However, also consider that around 50% of the US is liberal. They will be even more unprepared than the average Conservative.
I think the continuation of your excellent essay, Travis McGee, should incorporate survival strategies for people who make it through the first acute wave of attack. Reason being in another week they will be facing a second chronic wave of attack by their own neighbors, many of whom will be as similarly armed (in weapon and mindset). In the rural areas this is not an issue since food and water will be available and people will work together (eg half farming with the other half doing protection duty), but that is not an option in suburbia.
If the system collapses, in the same way most black people will be killed by other black people (especially once excursions outside are met with hostile fire forcing the mobs to fall back to their home turf), most white people will be killed by other White people.