Now, to be fair, the Americans lost very, very few people in WW1 compared to the other nations involved. And unlike the UK, France, Germany etc. they had recently had a war in which they lost way, way more people. I can really understand why it is smaller in their memory.
Edit:
US deaths by war (all causes):
American Revolutionary War: appx 25,000
War of 1812: appx. 15,000
Mexican-American War: 13,283
American Civil War: appx. 750,000
Spanish-American War: 2446
World War I: 116,516
World War I: 405,399
I mean, there's a huge difference there. Look at the UK by comparison:
American Revolutionary War: appx 24,00
Napoleonic Wars: 311,806 (incl. War of 1812)
Crimean War: 21,097
Boer Wars: 21,552
First World War: 826,746 (UK only)
Second World War: 450,900
It's even crazier when you look at France:
American Revolutionary War: appx 10,000
Napoleonic Wars: appx 1,771,000
Crimean War: appx 95,000
French Intervention in Mexico: 6,654
Franco-Prussian War: 138,871
World War I: 1,357,000
World War II: 550,000