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.

2000/bmeyer/README.md

@@ -373,7 +373,7 @@ en/decoded\[4\].
 
 - [lavabus.pgm](lavabus.pgm)
 
-    A bus that was trapped by lava from Kilauea volcano in Hawaii, USA.  Nobody
+    A bus that was trapped by lava from Kilauea volcano in Hawaii, US.  Nobody
     was in the bus at the time, BTW.  Photo date: 1981.
 
 - [lenna.glic](lenna.glic)

2000/dhyang/README.md

@@ -4,7 +4,7 @@ Don Yang
 UCSD  
 259 E. Bellbrook St.  
 Covina, CA 91722  
-USA  
+US  
 <http://uguu.org>   
 
 ## To build:

2000/dlowe/README.md

@@ -3,7 +3,7 @@
 David Lowe  
 1224 11th Avenue  
 San Francisco, California, 94122  
-USA  
+US  
 
 ## To build:
 

2000/robison/README.md

@@ -3,7 +3,7 @@
 Arch D. Robison  
 1406 Country Lake Drive  
 Champaign IL 61821  
-USA  
+US  
 
 ## To build:
 

2000/schneiderwent/README.md

@@ -1,7 +1,7 @@
 # Most Timely Output
 
 Craig Schneiderwent  
-WI, USA  
+WI, US  
 
 ## To build: