Mataj, when you post Warsaw, I'm assuming you're in Poland, and you're wondering why in the world would Americans use an old German military symbol!!

It's one of those things where someone, possibly or probably not knowing the original significance of the symbol, thought it looked cool! It probably slipped into our usage sometime after WW1. Whether it was a hot rodder or a biker who started using it first is no longer clear, but the use of the iron cross has endured over the years and has enjoyed some renaissance, particularly with the "rat rod" crowd. I'm sure it's partly an irreverence thing!!

Hopefully I've explained it well enough. Your english is way better than my Polish.................since I don't know any.