During WW2 the US was behind severely in small arms and initially relied on old Springfield rifles until the M1 arrived and the Carbine version. But they came across the German assault rifles after D-Day and marveled at the STG-44 which also became the basis for the postwar Soviet AK-47 (of which over 60 million copies can be found all over the earth). Now in 2013, the Iraq and Afghan Wars proved that the Colt M4 is a POS and that US troops wanted the German XM8 which was basically a HK G-36 built to US specs and in conjunction with ATK. It was going to win the ACR competition but for a third time Congress halted it and bailed-out Colt again in 2006. HK angrily responded with the 5.56mm HK-416 and the 7.62mm HK-417 which are used with US SFs along with the Belgian FN(H) SCAR. SOCOM forces use German HK SOCOM .45 pistols, HK UMP 45 SMGs, HK P-11 underwater pistols, and HK MP-5s (of many configuations). Rheinmetall AG has been working on a new plasma rifle since 2003...

STG= Sturmgewehr or Assault Rifle (personally named by Hitler himself in WW2)