The President of the United States is the Commander in Chief, who is responsible for all final decisions. The Secretary of the Department of Defense (DoD) has control over the military and each branch - except the Coast Guard, which is under the Dept. of Homeland Security. With over 2 million civilian and military employees, the DoD is the world's largest "company."
As of 2017, the U.S. spends about US$610 billion annually to fund its military forces and Overseas Contingency Operations. Put together, the U.S. constitutes roughly 40 percent of the world's military expenditures. The U.S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enables a widespread deployment of the force around the world, including around 800 military bases outside the United States. The U.S. Air Force is the world's largest air force, the U.S. Navy is the world's largest navy by tonnage, and the U.S. Navy and the U.S. Marine Corps combined are the world's second largest air arm. In terms of size, the U.S. Coast Guard is the world's 12th largest naval force. 
On 3 December 2015, U.S. Defense Secretary Ashton Carter announced that all military combat jobs would become available to women. This gave women access to the roughly 10% of military jobs which were previously closed off due to their combat nature. The decision gave military services until January 2016 to seek exceptions to the rule if they believe that certain jobs, such as machine gunners, should be restricted to men only. These restrictions were due in part to prior studies which stated that mixed gender units are less capable in combat. Physical requirements for all jobs remained unchanged, though. Many women believe this will allow for them to improve their positions in the military, since most high-ranking officers start in combat positions. Since women are now available to work in any position in the military, female entry into the draft has been proposed.