The reason some vegetables (particularly tomatoes) taste fairly subpar in the United States is because of the journey they make to reach your salad. If the tomatoes are coming from across the country (or Mexico, or another nation) they are actually picked prematurely so instead of ripening on the vine they ripen during transit. If you've ever had a tomato that tastes "mealy" this is the reason.

This mass transportation of food over long distances explains why you can get an orange any time of the year in Boston but also why the quality can be so poor - you're far away from the source.

After moving to San Francsico (from Boston with it's crazy winters) where local produce is available pretty much year-round at the local food Coop, I've noticed a pronounced different in the average quality and notably lower prices.