most Americans don't fly

I'm not sure that's actually true. According to the Bureau of Transportation Statistics, there were 646 million enplaned passengers in 2013. ("Enplaned passengers" means passengers boarding originating flights, i.e., either nonstops to the destination or the first leg of an itinerary with at least one connection.) That's more than twice the population of the US, and about 2.7 times the population of the US that's over 18. Even allowing for the fact that many business travelers take many trips per year, there are still a lot of people who only take one or two airline trips per year, for vacations or special events, so it's hard for me to see how the percentage of Americans who don't fly can amount to "most"; I'd be surprised if it was half.

BTS link: http://www.transtats.bts.gov/

if you started creating or enforcing speed restrictions or drunk driving there'd be endless Libertarian arguments about the perils of big government, and the "freedom" of motor cyclists to not wear a helmet if they so choose

I think you're seriously underestimating the costs of enforcing driving regulations to the extent that you would need to to improve the numbers significantly by that means; I suspect that a more realistic estimate of those costs is what would lead most people (including me) to oppose such regulations. Whatever one's opinion about airport security, the amount spent on it is still a small fraction of government budgets and an even smaller fraction of GDP; and even for business travelers that take many trips per year, the overall cost in time of security screening is not that much compared to the time spent on the flight itself, particularly since most business travelers are easier to screen since they're familiar with the process and so get through it more quickly than people who only fly occasionally. (Note that I'm not arguing here that what is spent is justified by the benefits; I'm merely trying to compare the cost of airport security, in both time and money, with the cost of the sort of traffic regulation you're proposing.)

On the other hand, the kind of regulation you would need to have in order to, for example, make a serious dent in the rate of speeding, would be extremely draconian and would have huge costs. You would need traffic police on every major road, stopping people left and right; and you would need to do this continuously, or at least often enough that people would have a fairly high probability of getting caught if they speed. After all, most people do not speed just for the fun of it; they speed because it benefits them, because they get to wherever they are going faster. (I would also argue that most speed limits on highways are set too low, particularly given how the performance and handling of cars has improved over the years.) To make people not speed, you would have to raise its costs, in money and time lost, enough to outweigh the benefits, and that's a very tall order. Plus, you would have to hire all those traffic police, and pay them, and all the time they spend catching speeders would not be spent dealing with other issues that might actually be more important.

Similar remarks apply, although possibly with less force, to other types of regulations: for example, trying to enforce seat belt laws, or motorcycle helmet laws, or drunk driving laws. I say "possibly with less force" because the "benefits" to people of doing these things are less clear than the obvious benefit in time saved of speeding. I don't understand any more than you do why anyone would fail to use a seat belt; it only takes a few seconds to buckle up. (I don't ride motorcycles so I won't try to speculate on why people would not wear helmets.) People obviously derive pleasure from drinking, but that doesn't mean they necessarily derive pleasure from drunk driving; that seems more like bad planning than anything else. So it might not be quite as costly to try to regulate these behaviors as it would be to try to regulate speeding. But I think it would still be a lot more costly than airport security is.

Education is a different matter; but I'm not sure there's much that can be done with education that isn't already being done. Are there really many people who haven't been told that seat belts are a good idea?

The only other suggestion I have is to impose more severe consequences on the kinds of decisions that can significantly affect risk. For example, consider this modest proposal: if you are involved in any accident and you are found to be driving drunk, even if no one is injured or killed, you lose your driver's license, forever. Or consider this: allow auto insurance companies, and health insurance companies to the extent that their coverage extends to injuries suffered in auto accidents, to make you pay a higher deductible, or possibly even deny part or all of your coverage, if you are injured in an accident and are found not to have been wearing a seat belt, or you are found to be at fault and to have been driving at a clearly unsafe speed. (This would have to be explicitly stated in the policy, of course.) That would make people stop and think.