What brought about economic prosperity in the united states and how did it affect most americans?

As the commenter commented, it's important to know what time period you have in mind with the question. 

But let's pick a time period -- the postwar boom in the American economy after World War II.  If you want to look at a period where American prosperity grew rapidly, that was a time of dramatic growth.  The overall US economy grew 37% during the 1950s.  Some of the things that generated such dynamic activity in the country were:
... The GI Bill, which helped military veterans get a college education, so you were preparing a large workforce of educated, skilled workers.
... Major infrastructure projects, such as the building of interstate highways. And while the federal government pumped billions of dollars into the Federal Aid Highway Act (1956), the Eisenhower administration also managed to keep the federal budget in balance, and inflation and unemployment remained low.
... Cheap oil was available from domestic oil production.
... Potential industry competitors in Europe were slowed by their efforts to rebuild life on that continent after the ravages of World War II.

Americans' standard of living grew in similar proportion to the country's economic growth.  A typical American family had 30% more buying power at the end of the 1950s than they did when that decade began.