^ No nuclear weapons involved either, but still a war between the US and Great Britain erupting in 1859 would have probably "messed up" history as we got to know it beyond all recognition
The British sent 5 warships with more than a thousand soldiers into the region. The US sent the 9th infantry led by George Edward Pickett (the same one who became associated with "Pickett's charge during the battle of Gettysburg four years later). Both sides tried to taunt the other into opening fire but neither complied. At last the British admiral suggested that it was kind of silly to start a war about a killed pig and everyone agreed.
The debate about the ownership of the island continued into the 1870s though when Germany was chosen as an unbiased judge on the matter. The verdict of the Germans was very much in favor of the US who got all of the disputed islands. [history lecture mode off]
El Salvador