Gee I guess I didn't need all of those years studying military history at university after all. Thanks for the crash course.

The last declared war the USA participated in was WWII.

I'll count most of the many conflicts the US military has engaged in since 1945 as wars in keeping with common usage.

Winning a war means achieving strategic objectives. It doesn't mean just blowing things up and killing people. Whether the failure comes from lack of military capability or failure of political will makes no difference when a civilian government controls the military, and sets the strategic (and sometimes tactical) objectives.

The four big conflicts since 1945 didn't go well. Korea drew to a stalemate. True, South Korea still exists, but so does North Korea. The American strategic objective -- preventing communist takeover of Korea -- was only partly achieved. After the war South Korea suffered under military rule and dictators until the late 1980s

The same strategic objective got us into Vietnam, a war we clearly lost. That war sapped political and public confidence to such a degree that the US allowed a horrible genocide to happen in Cambodia. Vietnam had to intervene.

The First Gulf War, a police action to protect Kuwait from invasion, went well except the US failed to follow through and disable Saddam Hussein's ability to fight another day, which led to a second war predicated on lies and no clear strategic objective. The USA did topple Hussein, but destroyed the country and its infrastructure in the process, and set the stage for ISIS and other terrorist groups still operating there.

Afghanistan didn't have clear strategic objectives, the justifications changed repeatedly. And the USA lost.

The Kosovo War ended by NATO action. The USA led by President Clinton intervened. Strategic objectives met, we can call that a victory.

Grenada and Panama were minor rescue operations and police actions; I hesitate to call those "wars." Panama was invaded to depose and arrest a single man, Manuel Noriega, a former CIA puppet who (like Saddam Hussein) turned on his former patrons. I think of those as Bay Of Pigs type small-scale actions, except the US succeeded in Grenada and Panama.

You left out Somalia, another UN/USA operation that ended with the US evacuating.

I agree that a lot of potential conflicts -- Taiwan, Iran, North Korea -- have not erupted because the United States does have tremendous military capability, reaching around the world, and that has a real and effective deterrent effect on nation states. It has not deterred Russia, though. It has less value deterring terrorists and non-state actors such as ISIS, the Taliban, Houthi rebels, communist rebels in the Philippines, and Mexican drug cartels.