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.

1990/cmills/README.md

@@ -4,7 +4,7 @@ Chris Mills
 Wyse Technology  
 3471 N. 1st St.  
 San Jose CA 95134  
-USA  
+US  
 
 ## To build:
 

1990/dg/README.md

@@ -4,7 +4,7 @@ David Goodenough
 anonymous organization   
 541 Commonwealth Ave  
 Newton, MA 02159  
-USA  
+US  
 
 ## To build:
 

1990/jaw/README.md

@@ -5,19 +5,19 @@ Research Institute for Advanced Computer Science
 MS 230-5  
 NASA Ames Research Center  
 Moffett Field, CA 94131  
-USA  
+US  
 
 Karl F. Fox  
 Morning Star Technologies, Inc.  
 1760 Zollinger Road  
 Columbus, OH 43221  
-USA  
+US  
 
 Paul Eggert  
 Twin Sun Inc.  
 360 N. Sepulveda Blvd. #2055  
 El Segundo, CA 90245  
-USA  
+US  
 
 ## To build:
 

1990/scjones/README.md

@@ -4,7 +4,7 @@ Larry Jones
 SDRC  
 2000 Eastman Dr  
 Milford, OH 45150    
-USA  
+US  
 
 ## To build:
 

1990/tbr/README.md

@@ -4,13 +4,13 @@ Byron Rakitzis
 Princeton University   
 5707 Old Lodge Dr.     
 Houston, TX 77066      
-USA		       
+US		       
 
 Sean Dorward   
 Princeton University  
 10274 Burleigh Cottage Lane  
 Ellicott City, MD 21043  
-USA  
+US  
 
 
 ## To build:

1990/theorem/README.md

@@ -4,7 +4,7 @@ Adrian Mariano
 University of Washington  
 2729 72nd Ave SE  
 Mercer Island, WA 98040  
-USA  
+US  
 
 
 ## To build:

1990/westley/README.md

@@ -4,7 +4,7 @@ Brian Westley (Merlyn LeRoy on usenet)
 DigiBoard, Inc.  
 1026 Blair Ave.  
 St. Paul, MN  55104    
-USA  
+US  
 <http://www.westley.org>  
 
 ## To build: