Neither Germany nor Italy were unified countries at the time of the Civil War so you can rule out this answer. Britain considered that a divided United States would be good for its economic interests, but because the British public would never support joining the Confederacy in a war that was seemingly about slavery the British government could not get involved. France likewise wanted the American union to break up because it had colonial ambitions in the continent still. Russia, however, under Tsar Alexander (the man who freed the serfs) supported the Union. It is highly likely that the most important factor that prevented France and Britain from getting involved was the fear that this would lead to another war with Russia.

The Battle of Lepanto was a naval battle fought in 1571 between the Ottoman Empire and the Holy League (an alliance of Venice, the Spanish forces of Charles V, and the Hapsburg forces of the Holy Roman Empire). The battle can be most clearly understood as a battle between Catholic and Islamic Empires for control of the Mediterranean. It was a significant victory for the Catholic forces. 

John Cabot was an Italian explorer who sailed for the New World in 1497 (just five years after Columbus' voyage) under the sponsorship of King Henry VII of England. He is generally considered to be the first European to set foot on the American mainland. Columbus, although widely credited with being the first European in the Americas, never made it past the Caribbean. It is also possible that Cabot may not be quite deserving of the credit bestowed upon him, as many historians consider it likely that the Vikings arrived in North America sometime in the eleventh century.

The Battle of Austerlitz is one of the most famous land battles of the Napoleonic Wars. The French forces of Napoleon defeated the combined armies of Austria and Russia and gave France control of most of the European continent. The Battle of Trafalgar is one of the most significant losses for Napoleon during his decade-long attempt to conquer Europe. It was a naval battle won by the British navy (led by Lord Admiral Nelson) that resulted in the annihilation of the French navy.

Albrecht von Wallenstein was a military commander from Bohemia who fought for the Holy Roman Emperor against the armies of Northern Protestantism during the Thirty Years' War. He was a highly succesful leader who won many battles, but his ambition and success began to worry the Emperor, who subsequently had him assassinated.

The Columbian Exchange describes the widespread exchange of animals, human populations, cultures, religions, diseases, and plants between the Old World of Europe, North Africa, and Asia and the New World of North and South America. It took place, primarily from the late fifteenth century through the seventeenth century and changed the very nature of the human experience.

Napoleon III was defeated and captured by the Prussians in the battle of Sedan in 1870, and was formally removed from office several days later. Both Waterloo and Leipzig were battles fought by Napoleon I over five decades earlier. Sebastopol was a battle fought in the Crimean War in the 1850s. Verdun was a battle fought in World War I, long after the downfall of Napoleon III.

In the Franco-Prussian War of 1870-71, the German states led by Prussia defeated France, and in the peace negotiations that followed, the German states all agreed to unite under the Prussian monarchy. The Seven Years' War occurred over a century before, and simply saw Prussia secure its position as a major European power. The Congress of Vienna in 1815 concluded the Napoleonic Wars, and saw Prussia merely re-establish a powerful position in European affairs. The Revolutions of 1848, including German nationalistic uprisings, all ended in failure, and did not lead to unification. World War I was fought in the 1910s, long after Germany had united under Prussia.

While Louis XIV was an absolutist monarch who sought to curtail the power of the nobility, he was only successful in this to a degree, and did not abolish their special privileges (that, namely, kept them largely exempt from royal taxes). Louis and his ministers did, however, enact a number of military and administrative reforms designed to strengthen both the French military and the French royal government. Louis also had the impressive Palace of Versailles built, where he not only kept most of his government but his lavish court, which he used to distract the nobility from interfering with his ambitions. With the conquest of Alsace and other areas to the east, Louis also extended French territory to the Rhine river, and oversaw expansion of the French colonial empire, mainly in North America, India, and the Caribbean.

While the Thirty Years' War was a major victory for Protestant European states and confirmed the principle that sovereign rulers could decide the official religion of their state without outside interference, it did not cause all of the German states to adopt Protestantism, as many of them (such as Austria and Bavaria) remained Catholic. In confirming the principle that states should be free from foreign interference in religious affairs, the war was the last major European conflict in which religion was a major factor, and from this point international affairs and conflicts were focused mainly on secular matters such as territorial expansion, the balance of power, and colonial rivalries. As the war saw the defeat of the Catholic Habsburg states by France and its Protestant allies, namely Sweden, it led to the further decline of Habsburg power, France replacing Spain as the dominant military power in Europe, and Sweden securing its position as a major European power.