Is it true US warships enforced the blockade during the 1962 Cuban Missile Crisis by sinking all Soviet-flagged vessels approaching the island?

No, it is not true that US warships sank all Soviet-flagged vessels during the 1962 Cuban Missile Crisis. While the US did enforce a naval blockade to prevent Soviet ships from delivering military supplies to Cuba, they primarily used a strategy of interception and inspection rather than sinking vessels. Most Soviet ships either turned back or were allowed to pass after being inspected. The crisis was ultimately resolved through diplomatic negotiations rather than military confrontation.