I know one American who honored this tradition. I never did research for more details, but I knew it honored vets, he 'fallen'. My dad always wore a poppy, he also would be selling them around this time of the year. He wasn't part of a legion or anything either. Hmmmm, now I wonder not why he did this, but 'how' it evolved, what or who pulled him in to the poppy idea. Whereas, he never bothered to visit the graves of relatives on Veteran's Day, my mom always did that alone, or with her sister.
Anyway, some Americans do honor the fallen with poppies. I don't go out looking for them at this time, but when I run aross someone selling them I buy one. I have even started planting poppies, I thought it was in memory of my dad. Now it will have more significance.
Certainly, the act of wearing a poppy shouldn't be any less significant because we're Americans, huh? All of the fallen (from present to years' past) should be recognized and honored by all!