In America, punctuality is an interesting topic.  In some spaces like jobs and schools, the people in charge expect you to be on time.  HOWEVER, because America is populated by many different cultures, many people will tell you that punctuality is not that important.  To be frank, it is the spaces that are run by Caucasians (Western European descendants) that are the most likely to enforce punctuality while the spaces run by minorities are less likely to enforce punctuality.  This  includes being on time and also starting things on time.  Sometimes, it can be difficult to do work with a diverse group of people!  I was very grateful when I was hired by a company that let me arrive at work whenever I wanted to.

EDIT: In many places, relationships are more important than timeliness.  This is true of Spanish-speaking countries, right?  Many people who come to America maintain that focus on relationships and pass that trait on to their children.