You need to stop sleeping through history class.
I'm American myself, and I know that's not true. Technically we didn't even start the last two you mentioned, being the Confederated States of America declared war on the Union, and the Japanese attacked the US without declaring war, making the US join WWII. We didn't even kill Hitler, he commited suicide when Germany lost the war.
(The dates of the wars below are listed by when the US joined to when the war ended, not when it was started)
Here are the wars I can name when the United States started them:
• American Revolutionary War, 1775-1763
• War of 1812, 1812-1815
• Mexican-American War, 1846-1848
• Spanish-American War, 1898-1898
Wars the US was in they didn't start:
• American Civil War, 1861-1865
• World War I, 1917-1918
• World War II, 1941-1945
You're welcome. And to you non-Americans out there, some Americans can be smart and think about more than just hamburgers