Factory work was not yet as common place as America and England in many other countries. Ford assembly lines were not yet widely used when WW1 broke out, most of the WW1 was fought with less industrialized weaponry.
That's partly it, but what I really meant was that America didn't have many combat casualties, relative to other countries. 53,400 according to Wikipedia, which was less than Canada's 56,600, and much less than France's 1,150,000 or Germany's 1,800,000.
The US basically wasn't a major combatant in that war, so it's not a representative country to use as an example. I'm sure it does show that factory conditions were brutal, but it falsely implies that they were more brutal than combat conditions.
"More Americans died in making stuff for the WW1 than in the actual war, as the conditions of factory work was brutal."
I'm doubtful that this is true for many other countries involved in that war.