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.

2004/burley/README.md

@@ -3,7 +3,7 @@
     Brent Burley
     500 S. Buena Vista St.
     Burbank, CA 91521
-    USA
+    US
 
 ## To build:
 

2004/hoyle/README.md

@@ -3,7 +3,7 @@
     Jonathan Hoyle
     162 Burwyck Park
     Saline, MI  48176
-    USA
+    US
 
     http://www.jonhoyle.com
 

2004/jdalbec/README.md

@@ -3,7 +3,7 @@
 John Dalbec  
 20 Squire's Ct.  
 Canfield OH 44406  
-USA  
+US  
 <https://jpdalbec.people.ysu.edu>  
 
 ## To build:

2004/omoikane/README.md

@@ -3,7 +3,7 @@
     Don Yang
     259 E. Bellbrook St.
     Covina, CA 91722
-    USA
+    US
 
     http://uguu.org/
 

2004/vik1/README.md

@@ -3,7 +3,7 @@
     Daniel Vik
     926 Genter Street
     La Jolla, Ca 92037
-    USA
+    US
 
     http://www.vik.cc/
 

2004/vik2/README.md

@@ -3,7 +3,7 @@
     Daniel Vik
     926 Genter Street
     La Jolla, Ca 92037
-    USA
+    US
 
     http://www.vik.cc/