How effective has propaganda been in the United States? What about other countries?

by Aqec

Just as the title says,

How effective has propaganda been in the United States? What about other countries?

Have there been any historians who have written about this? If you have any recommended books or authors let me know/source them in your answer.

Thanks a bunch!

bojun

You have to define a better metric. What do you mean effective and how do you quantify it?