The subject is just a bit silly. The United States won a whole lot of wars on its own. Most of them extremely small wars. Can't think of too many modern countries who won big ones on their own, not lately, anyway. I suppose Vietnam defeated the U.S.
Hey Doug! If we had gone all out and "won" in Vietnam, does anyone imagine the world would be a better place today? In exactly what respect would the world be better off? Enough to warrant 10,000 more dead? 100,000? A war with China? I recall Barry Goldwater wanted to use the atomic bomb. Would we be better off if that had been done?
But now, people forget that at the time of the war with Mexico, Mexico was not a small nation. Not by comparison. The Mexican Army was about 4 times as large as the United States Army. Winfield Scott walked right into the middle of Mexico, and if he had lost a single battle he would have been destroyed. He did not lose a single one. The Duke of Wellington, not known for his modesty, called Scott the greatest living general. Among Scott's junior officers were Lee, Jackson, Grant, Longstreet, and Beauregard. If you want to brag about military achievements, that was one.
But are we really sure we want to brag all that much about military achievements. The kind of country that is best at winning wars is not the necessarily the best one to live in. A friend of mine in grad school wrote a doctoral dissertation comparing the southern slaveholder to the Prussian Junker. Very strong parallels there. Those guys make fine soldiers. Lots of military virtues. Maybe one should cultivate other virtues as well -- or instead?