Write SQL query to solve given problem: Which of the American customers have experienced a delay in the shipment and how long was the longest?. Keep the solution inside sql tag ```sql [SQL-Query] ```
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