Afghanistan: The U.S. has been involved in the war in Afghanistan since 2001, following the September 11 attacks. The war has been waged primarily against the Taliban, an Islamist militant group that once controlled much of the country. While the U.S. and its allies initially removed the Taliban from power and established a new Afghan government, the Taliban has since regained significant control over the country. Peace talks between the Taliban and the Afghan government have been ongoing, but progress has been slow.
Iraq: The U.S. invaded Iraq in 2003, overthrowing the government of Saddam Hussein. The initial invasion was followed by a protracted insurgency and sectarian conflict. The U.S. withdrew most of its troops from Iraq in 2011, but returned a small force in 2014 to help the Iraqi government fight the Islamic State of Iraq and the Levant (ISIL), also known as ISIS. ISIL has since been largely defeated in Iraq, but the U.S. continues to provide training and support to the Iraqi military.
Syria: The U.S. has been involved in the Syrian Civil War since 2014, when it began airstrikes against ISIL targets in Syria. The U.S. has also supported rebel groups fighting against the government of Syrian President Bashar al-Assad. The U.S. has not directly intervened in the civil war, but has provided military and humanitarian assistance to various groups.
Yemen: The U.S. has provided logistical and intelligence support to the Saudi-led coalition that is fighting against the Houthi rebels in Yemen. The war in Yemen has caused a severe humanitarian crisis, and the U.S. has been criticized for its role in supporting the coalition.
In addition to these conflicts, the U.S. is also engaged in counterterrorism operations in other countries, such as Somalia and the Philippines.