Why did the USA announce the Monroe Doctrine? What was the message to European nations?

The European powers, according to Monroe, were obligated to respect the Western Hemisphere as the United States' sphere of interest. President James Monroe's 1823 annual message to Congress contained the Monroe Doctrine, which warned European powers not to interfere in the affairs of the Western Hemisphere.

Explanation:

abraham lincoln  (february 12, 1809  – april 15, 1865) was an american statesman, politician, and lawyer who served as the 16th  president of the united states  from 1861 until  his assassination  in april 1865. lincoln led the nation through the  american civil war, its bloodiest war and its greatest moral, constitutional, and political crisis.[2][3]  he preserved the  union,  abolished slavery, strengthened the  federal government, and modernized  the u.s. economy.

after defeating german forces in north africa allied leaders turned their attention to "italy," since this was the location that made the most geographic sense before invading northern europe via france.