http://en.wikipedia.org/wiki/War_of_1812
Ancient history, I know. I'm just that much of a historical geek, I admit.
A matter of sovereignity was decided by this conflict with our brothers & sisters across the pond. No longer would American flagged vessels be stopped on the high seas and find their crews involuntarily impressed into the British Navy.
The Brits kept it on the down low until Emperor Napolean's defeat in 1814. Then they landed armies on our shorelines once more and in a spectacular defeat they burned our capital down after partying in the White House on wine left behind by Abigail Adams and soiled her drapes wiping their backsides. Once they had their fun they torched the White House. While they were watching this spectacle a storm of almost biblical proportions descended upon them. Reports state that there were more casualties from the storm than from the Battle of Bladensburg (popularly called the Bladensberg Run!) The American troops had been victims of their own command. They were force marched all over the countryside following leads as to where the Brits were coming from. The meager tired troops were facing well rested and capable veterans of the French campaigns. The retreat into D.C., rout actually, was called The Bladensburg Run as the Brits came into the capital down Bladensburg Road. Our troops were panicing and tossing their weapons down running like hellhounds were after them.
Some reports of that storm described a tornado. It must have been extremely demoralizing to the victors. They were scattered all over the map and suffered many dead from a storm. They backtracked to their ships more or less unhindered and took some time refitting and recuperating down in the Caribbean.
They continued fighting us and culminating in the infamous (for the Brits) Battle of New Orleans. Where the American irregular militias for once stood their ground and handed these tough veterans of the war with the French a trouncing that they couldn't really recover from. It was a defeat that the British Army had never experienced before, let's just say since 1066 A.D., when King Harald got himself killed by the Normans.
In the end we agreed to the ante bellum conditions and boundaries that existed. In addition we won recognition by the Court of our rights as a sovereign country.