Would not Fr Emil Kapaun, a Catholic priest and US Army chaplain, who died in 1951 in a North Korean POW camp, not be the first US martyr?  His story is not too dissimilar from that of St Maximilian Kolbe.  Kapaun, like Kolbe, put his fellow prisoners needs before his own.  He was recognized as a "Servant of God" by Pope St. John Paul II in '93.  It seems that his cause is sadly discounted because he was a military chaplain who was more highly decorated by the US Army than by his own Church.