napoleonic wars
The collective name for a series of global wars between 1803 and 1815, between France under Emperor Napoleon Bonaparte and its allies and a series of European coalitions.
Though the coalitions were in the end able to finally defeat Napoleon, his campaigns across the continent decisively altered the balance of power in Europe. The Holy Roman Empire was finally destroyed, and the empires of Spain and Portugal were severely weakened. But the wars brought France back onto the world stage for the first time since the French Revolution, cleared the way for Prussia for amass strength in the center of the continent, paved the way for the unification of Italy and German Empire, and turned the United Kingdom into the center of world trade and commerce.
It also allowed a great deal of breathing room for the new nation of the United States to develop unhindered by powerful foreign interests. The destruction of European empires also allowed the US to step in as the foremost power in the Western Hemisphere, and could rapidly expand in size by gobbling up land purchased from or abandoned by Europeans with concerns closer to home.