The Trent affair caused war between Britain and the U.S.
Huge cotton inventory & new sources of cotton made Britain less reliant on southern cotton, and thus less likely to support the southern war effort.
Britain accumulated a large supply of cotton before the war, so they didn't need any more and found new sources of cotton in Egypt and India.
Europe's wheat crop failed, so Northern wheat&corn replaced cotton as an essential import.
Two confederate diplomats, Mason and Slidell, were on their thanks to Europe to do once more for support on a British bottom after they were stopped by General Wilkes on the San Jacinto and in remission.