Which of the American customers have experienced a delay in the shipment and how long was the longest?
"American" refers to Country = 'USA'; longest delay in shipment refers to Max(Subtract(RequiredDate, ShippedDate)); customer refers to CustomerID
SELECT T1.CompanyName, TIMESTAMPDIFF(DAY, T2.ShippedDate, T2.RequiredDate) FROM Customers AS T1 INNER JOIN Orders AS T2 ON T1.CustomerID = T2.CustomerID WHERE T1.Country = 'USA' AND TIMESTAMPDIFF(DAY, T2.ShippedDate, T2.RequiredDate) < 0