Why does Roosevelt say that America should not assume that they have time to prepare and that the Atlantic Ocean will prevent an invasion?

To designate young isolationists, who deluded themselves into believing that America could remain aloof, secure, and distant from the wars raging in Europe, Roosevelt liked the amusing term "shrimps"-- crustaceans possessing a nerve cord but no brain. In that critical month of May 1940, he finally realized that it was probably a question of when, not if, the United States would be drawn into war. Talk about neutrality or noninvolvement was no longer seasonable as the unimaginable dangers he had barely glimpsed in 1936 erupted into what he termed a "hurricane of events."Explanation: