Russian annexation of Crimea
When Russia forcibly annexed Ukraine's Crimean Peninsula in 2014, their actions were strongly denounced by many nations, especially the by the U.S. and European Union. America refused to recognize the Kremlin's sovereign claim over Crimea and even imposed sanctions on Russia (like many other Western nations) to match their strong condemnation of Russia's illegal actions. This Russian annexation of Crimea and the U.S. sanctions that resulted from such an action, both actively contributed to a more unwelcoming relationship between these two nations. Their increasingly chilly relations over international and financial issues connected to this Crimea annexation only works to resurge Cold War relations.