NEW YORK – All-American classics have always been J. Crew’s forte. But for spring, Emily Woods, the company’s vice chairman, has infused the Collection line she designs with a more sophisticated spirit. The clothes have the simple, fluid shapes, meticulous construction and gentle, neutral tones suggestive of European lines such as Prada, Agnes B. or A.P.C. Everything in the line – from underwear to eveningwear – is available exclusively in the 28 J. Crew stores.