When German submarines started sinking British ships who asked for us help?

Yes, the above answer is correct. But I believe it was Winston Churchill's Rapport with the President of America, Franklin Delano Roosevelt, that led to the USA coming to the help of Britain and her Allies. At first it was lease-lend - helping with old ships, etc, but in return in Britain allowing America to set up facilities in British held territories. But, once Japan attacked Pearl Harbour, America were able to publically declare war - and America geared up to help Britain and the Allies in defeating Germany, and Japan.