Based on your expert opinion from hundreds of miles away? I'm simply trying to eliminate ANY mechanical problems since that's probably the easiest thing to determine since it's objective.
Um, no... not based on my expert opinion... but nice that you think I'm an expert! (See? I can be sarcastic too. 
)
No, based on real statistical odds which, I (mistakenly) assumed are common knowledge. To remedy that mistake, I offer the following excerpt from an article posted by The Center for Internet and Society at Stanford Law School (Human error as a cause of vehicle crashes | Center for Internet and Society)
- (1) The most thorough analysis of crash causation, the Tri-Level Study of the Causes of Traffic Accidents published in 1979, found that "human errors and deficiencies" were a definite or probable cause in 90-93% of the incidents examined. The executive summary is here (see vii), and the two-part final report is here and here. The study continues to be cited, and the Venn diagram on this page provides a useful summary.
- (2) A UK study published in 1980 (summarized here at 88-89) likewise identifies driver error, pedestrian error, or impairment as the "main contributory factor[]" in 95% of the crashes examined.
- (3) Another US study published in 2001 (available here) found that “a driver behavioral error caused or contributed to” 99% of the crashes investigated.
- (4) An annual UK crash report (available here with updated data here in table RAS50002) identifies 78 potential contributing factors, most of which suggest human error. However, multiple factors were recorded for some crashes, and none were recorded for others.
- (5) NHTSA’s 2008 National Motor Vehicle Crash Causation Survey is probably the primary source for the common assertion by NHTSA officials that “[h]uman error is the critical reason for 93% of crashes” (at least if “human error” and “driver error” are conflated). The 93% figure is absent from the report itself (probably intentionally) but calculable from the totals given on page 24.
So, as I said, THE ODDS favor driver error. I was not criticizing you or your driving ability and I was not offering an opinion, expert or otherwise. Since we have nothing to go on other than speculation, I was only stating that the odds favored driver error, not mechanical failure. Perhaps something did fail. Perhaps you couldn't turn away from the tree because the wheel linkage had already started to fall apart and the tree just finished the job. Perhaps, perhaps, perhaps... All speculation. However, as you stated from the beginning...
Tried to get it under control but my main concern was to avoid rolling and not hitting other vehicles. Ended up going off the highway and into a tree. Luckily, I did not hit any other vehicles and no one hit me as I swerved across traffic.
...so we have to assume you had some degree of control and the steering was working before you went off the road. Again, that is just speculation. You seem pretty convinced that you did nothing wrong when, if you really think about it, you probably did. Whatever happened to initiate the wheel slip is not the cause of the accident. The failure of the traction control, assuming it did fail, or the failure of any other safety system, is not the cause of the accident either. These systems only assist the driver's recovery efforts; they are not responsible for making recovery efforts for the driver.
So, like the statistical majority of all the other accidents that have been reported in the past 30+ years, both here and in other countries, the most likely cause of the accident (failure to avoid hitting the tree) was driver error. There's no shame in it. Obviously, you're not the only one. In fact, I've been in my fair share of accidents and I know there were things I failed to do to prevent it from happening because I wasn't expecting something to go wrong. That's how accidents happen. Also, it doesn't matter if something mechanical failed.
Years ago, I actually saw a guy in a 2-seat convertible roadster (1970's MG, I think) lose his rear wheel while driving in the third lane of a four lane highway. The lugs nuts scattered across the road and the entire wheel shot up a good 15ft. and went bouncing down the road to parts unknown. Somehow, the guy knew he was in trouble but still had the presence of mind to hit his turn signal and steer gently across 3 lanes of highway traffic and bring the car to a stop on the shoulder. We pulled up behind him as he jumped out and ran around to see what had happened, saw the wheel was not there, then broke down and cried his eyes out. He maintained control and didn't hit anyone or anything. Coincidentally, neither did the flying wheel. He didn't have any nanny systems helping him either. Maybe God was with him, but the rag top was down and I didn't see anyone else in the car.
In contrast, my own brother, a veteran motorcycle rider and certified motorcycle safety instructor for 19 yrs., fatally crashed his motorcycle and after assessing the damage to the bike I found there was no mechanical failure of any kind. Except for a bunch of dents, scrapes, bent handle bars and rims, everything was in working order. I searched the road for something he might have slipped on and, like you, I found nothing. It was warm, no rain, no traffic that we know of (a passing driver noticed the bike's headlight shining out of the woods onto the road and stopped to check it out), no solid evidence of anything that would cause him to lose control. It could have been a deer in the road because that area was know for such, but we'll never know for sure. The only thing I do know for sure is that something went wrong and he couldn't recover it. He laid the bike down, it slid off the road, and before he could get clear of the bike, the tires hit a root which launched both him and the his Harley Road King into the air and into the trees. I put the chain of event together based on the skid marks and the path of destruction the bike made from the time it left the pavement until it tumbled up against a tree, standing on its tires with its headlight casting its beam out toward the road. If not for the root, he might have had a chance but he had already made too many errors and his luck ran out.
Driver (rider, in this case) error was the cause of the actual accident. Was the guy that lost his car wheel lucky? You bet your bippy he was. But he managed to get the car safely off the road because he did not make a single error. Everything he did was deliberate, smooth, and perfectly executed. Was it skill or instinct? Don't know and it doesn't matter. He was the one driving so he gets all the credit. My brother was the one driving the bike so he gets all the credit too. It doesn't matter if the Slingshot's Traction Control failed, what matters is that as the driver, you failed to control the vehicle before it hit that tree. That was the accident, accidents happen, and they happen to newbies as well as skilled drivers (ever watch a NASCAR race?).
So, although you didn't ask for it, THAT is my informed (not expert) opinion on the matter. Unless there is some evidence that there was no possible way of avoiding that tree and that there was absolutely nothing you could have done differently to change the final outcome, driver error played a large part in the whole thing, whether you realize it or not. If it makes you feel any better, the odds are that at least 90% (probably more) of the other drivers that wrecked their Slingshots screwed up too, including me. Welcome to the club. 
