The U.S. as the Worlds Cash Cow

It has always been obvious to me that the United States buys its friend and allies.  And when the cash flow stops so does the friendship / alliance. Everyone wants U.S. dollars.  Its the methods of obtaining them that differs. Here is just the latest example of one of those methods, North Korea agreeing to disarm in exchange for financial considerations, or extortion  in my opinion.  Why is it that other countries can extort 
money from the U.S. thru veiled threats, but if you or I were to do it, you know where we'd end up, right?
 full story here