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.

1992/adrian/README.md

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

1992/buzzard.1/README.md

@@ -4,7 +4,7 @@ Sean Barrett
 Software Construction Company  
 430 Southwest Parkway, #1906  
 College Station, TX 77840  
-USA  
+US  
 
 
 ## To build:

1992/buzzard.2/README.md

@@ -4,7 +4,7 @@ Sean Barrett
 Software Construction Company  
 430 Southwest Parkway, #1906  
 College Station, TX 77840  
-USA  
+US  
 
 ## To build:
 

1992/lush/README.md

@@ -4,7 +4,7 @@ Ed Luke
 Mississippi State University  
 P.O. Box 6176  
 Mississippi State, MS 39762  
-USA    
+US    
 
 ## To build:
 

1992/nathan/README.md

@@ -58,7 +58,7 @@ The US International Traffic in Arms Regulations controls certain exportations
 going out of the United States.  The U.S.  Munitions List gives the specific
 categories of restricted exports.  Because this entry at one time appeared to
 fall under this restricted category, the judges originally were not able to
-distribute winners outside of the USA.
+distribute winners outside of the US.
 
 Nathan Sidwell stated that he was willing to distribute the winning source.  To
 read HIS instructions of how to obtain his winning program one was able to run:

1992/vern/README.md

@@ -6,7 +6,7 @@ Computer Systems Engineering
 Bldg. 46A, Room 1123  
 Lawrence Berkeley Laboratory  
 1 Cyclotron Rd.  
-Berkeley, CA 94720  USA  
+Berkeley, CA 94720  US  
 
 ## To build:
 

1992/westley/README.md

@@ -4,7 +4,7 @@ Brian Westley (aka Merlyn LeRoy)
 Digi International  
 1026 Blair Ave.  
 St. Paul, MN  55104  
-USA  
+US  
 <http://www.westley.org>  
 
 ## To build:
@@ -50,7 +50,7 @@ show correctly!
 
 ### Alternative code:
 
-The author provided a version for the USA. To build:
+The author provided a version for the US. To build:
 
 ```sh
 make alt
@@ -143,7 +143,7 @@ is reasonably accurate.
 - Beijing	    40   116
 - Tokyo		    36   140
 
-For a domestic (USA) version with higher resolution, try:
+For a domestic (US) version with higher resolution, try:
 
 ```c
 main(l,a,n,d)char**a;{for(d=atoi(a[1])/2*80-atoi(a[2])-2043;