One thing that hasn’t changed about combat since 2001 is that most of the American casualties, even in places like Iraq and Afghanistan have been non-combat. Actually, in that time less than 30 percent of deaths in the military were from combat and most of them did not take place in a combat zone but back in the United States. During the period of most intense combat (2001-2009) accidents, disease and stress (physical and mental) problems accounted for 81 percent of those troops flown out so they could get more advanced care. There are about ten of these evacuations for every soldier killed (combat or non-combat). Only 19 percent of those "medical evacuations" were for combat injuries. Thus, in the military hospitals (both in Iraq and Afghanistan, as well as back in the United States), the vast majority of combat zone casualties are not there because of combat injuries.
By 2009 American troops in Iraq had more to fear from accidents, disease and stress than enemy action. Less than half the troops who died were combat casualties. This is a trend that had been growing for several years. Actually, while not caused by combat, a lot of the "non-combat" injuries were the result of combat operations. For example, ten percent of those evacuated had musculoskeletal system problems. Since the 1990s American infantry has had to carry more weight (sometimes a 45 kg/a hundred pounds or more), more often and for longer periods. No one else in the combat zone had to deal with that. Back and muscle problems are still common.
The combat troops are also out and about more, and more likely to catch exotic local diseases. Thus it's not surprising that in places like Iraq and Afghanistan for a long time at least ten percent of the medical evacuations were for "ill-defined conditions." This was first discovered when thousands of American troops were stationed in the Persian Gulf during World War II. Before that, the British warned, from their World War I experience, that Iraq was a nasty place (from a disease standpoint) to hang out in. Afghanistan has proved to have its own extensive collection of exotic, and often unrecognized (by Western medicine) afflictions.
While most of the deaths (as opposed to casualties) in Iraq and Afghanistan were from combat, many were not. Of the 7,000 or so U.S. troops that died in Iraq and Afghanistan through 2018), nearly twenty percent of those fatalities were from non-combat causes. Most of the non-combat deaths were from accidents and disease. One of the major categories of non-combat death is vehicle accidents. In 2007, over fifteen percent of the non-combat deaths were from vehicle accidents. But in 2008, overall deaths declined by two thirds (from 904 in 2007 to 312 in 2008), and vehicle accident deaths went from 37 to 19. Over time better driver training, improved vehicle design and experience, in general, made driving less lethal.
The U.S. Army expected vehicle accidents to decline even more in 2008 because the number of terrorist incidents went down by 80 percent. Many vehicle accidents were the result of the fast driving tactics troops were encouraged to use to get away from roadside bombs and ambushes. Ask the NCOs, and they will often complain that the sharp reduction in combat has removed the incentive to stay sharp and pay attention. Not a unique situation in a combat zone, and despite the energetic exhortations of the NCOs, too many troops did not stay alert enough to avoid accidents. Ask the troops, and they will (correctly) complain about the heavier traffic. With peace breaking out all over central Iraq, and the economy continuing to boom, more Iraqis have cars. Iraqis drive like they're from Boston, with abandon and indifference. Not much different in Afghanistan.
Meanwhile, military experts around the world are still trying to make sense of how the United States has kept its casualties so low in Iraq and Afghanistan. To put it in simple terms, you were three times more likely to be killed or wounded in Vietnam (or World War II), compared to U.S. troops serving in Iraq. And then there is the mystery of higher non-combat deaths in Afghanistan. In Vietnam and Iraq, 19 percent of the deaths were from non-combat causes (accidents, disease, for the most part.) During World War II, 25 percent of the dead were non-combat. In Afghanistan, 29 percent of the deaths were non-combat, although that is rapidly changing as combat deaths increase. Afghanistan does have a greater variety of diseases, and nasty terrain (including the atrocious roads, many of them roads in name only).
What the U.S. did was put in well trained, led, armed and motivated troops and then supported them lavishly. Civilians were hired to do a lot of the menial jobs. Much effort was put into getting to know the local culture, and avoiding civilian casualties. That eventually won over enough Iraqis to undercut support for Islamic radicals (mostly Sunni Arabs angry at no longer being in charge, and minority Shia groups keen on setting up a Shia religious dictatorship).
But while the diseases and safety situation in the Middle East improved enormously since 2003, improvements came more slowly in Afghanistan. The many diseases, bad roads, hills and mountains remain a major hazard. Afghanistan will remain a dangerous place, even if no one is shooting at you.
Another item that is still a concern is bad data. No, not official deception but simply inept record keeping. Bad numbers are nothing new. For example, the Department of Defense used to report that the number of combat deaths in the Korean War was higher (by over 10,000 dead) than there actually were. This was because, early on, someone mistakenly added all the accidental deaths, world-wide, for the United States military, during the period of the war (1950-53), to the total combat dead. It wasn't until the 1980s that this got cleared up.
And then there are some bad numbers that will never be cleaned up. Friendly fire incidents in past wars were routinely misreported, usually at the lowest levels (friends of those who got shot or did the shooting.) Any attempts to get to the bottom of friendly fire statistics from old wars would open too may psychological wounds. Same with the misreporting of dead soldiers as "missing in action" during World War II. This was often done by the dead soldiers family, so the widow could collect the soldiers pay (which was higher than widow's benefits) for a while longer. There are a lot of bad numbers out there, and an interesting story behind many of them.