In the last 120 years (1890-2010), US had trade surplus three times. During these three periods, America was a armaments and war supplies vendor to the British Empire.
During South African Wars (1879-1902), the British Empire was fighting intense wars in South Africa, to gain control over new-found diamond and gold deposits.
WWI (1914-1918), WWII (1939-1945) were fought to retain colonies.
During WWI and WWII, US joined the war, after the combatants had started to run out of oil, energy, soldiers, money, armaments, et al.
Vietnam War, the Islamic Wars against Iraq and Afghanistan are being funded and fought by US to protect its own Oil-Dollar Empire. So, no ‘benefit’ to the US.
The show goes on, for now …