All war is a crime. Name me one war America started.
The War of 1812. (We attacked the UK over trade restrictions, among other things.)
The Mexican War. (We attacked Mexico to get California and the Southwest.)
The Vietnam War, and the U.S.-backed coup d'etat against South Vietnamese president Diem that preceded it. (The so-called Gulf of Tonkin Incident was a complete lie.)
The Iraq War. (I'm sorry, but it's a fact.)
In each of these wars, the president and Congress of the United States acted in what they believed to be the national interest. That being said, every aggressor nation claims to be acting in its national interest.
In any case, the question of who started what is not always clear-cut. While we technically started the War of 1812 (we declared war on Britain on 18 June, 1812 and invaded Canada on 12 July), certain circumstances leading up to our attack could be construed as acts of aggression on the part of the British Empire. Vietnam was a battle of World War III, part of the containment strategy against the Commuists in the USSR and China. And we had solid strategic reasons to take down the Saddam Hussein regime as part of our overall strategy against global fundamentalist Islam.
However, we fought the Mexicans in order to take California and the whole Southwest for our own. It was a war of conquest, plain and simple.
While I'm glad that we won in Iraq and in Mexico, and sorry we lost in Vietnam, the fact remains that none of those three countries ever attacked the U.S.A. We had our reasons for starting those wars, but we did start them, and any refusal to acknowledge that we did is intellectually dishonest.