Remove 'America' (A) from 'USA' :-)

This to make the country code consistent with mkiocccentry (and I guess
international standard country codes).

This affects many README.md files and (for one line) winners.csv.

1989/fubar/README.md

@@ -5,7 +5,7 @@ Sequent Computer Systems, Inc
 15450 SW Koll Parkway  
 Beaverton, OR  
 97006  
-USA  
+US  
 
 ## To build:
 

1989/paul/README.md

@@ -5,7 +5,7 @@ CIRRUS LOGIC, Inc.
 1463 Centre Pointe Dr.  
 Milpitas, CA   
 95035   
-USA  
+US  
 
 ## To build:
 

1989/robison/README.md

@@ -5,7 +5,7 @@ University of Illinois
 1304 W. Springfield Ave.  
 Urbana, IL  
 61801  
-USA  
+US  
 
 ## To build:
 

1989/vanb/README.md

@@ -5,7 +5,7 @@ Department of Computer Science
 University of Central Florida  
 Orlando, Florida   
 32816  
-USA   
+US   
 
 
 ## To build:

1989/westley/README.md

@@ -5,7 +5,7 @@ Starfire Consulting
 1026 Blair Ave.  
 St. Paul, MN    
 55104    
-USA  
+US  
 <http://www.westley.org>  
 
 ## To build: