Why is baseball considered such a quintessential US sport?
There are many factors that make many Americans think of baseball as "America's pastime."  Possibly the biggest factor is that baseball has been played for so long that it's history ties together generations of Americans through their common rooting interest in their favorite teams.  Another reason: baseball players became celebrities and figures in pop culture long before such a thing was common in other sports.  While baseball has lagged in growth in recent times when compared to leagues such as the NFL and the NBA, it is still a vibrant sport with large revenues and extremely passionate fan bases around the country.