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.

2001/bellard/Makefile

@@ -38,7 +38,7 @@ include ../../var.mk
 
 # Common C compiler warnings to silence
 #
-CSILENCE= -Wno-bitwise-op-parentheses -Wno-error -Wno-implicit-function-declaration \
+CSILENCE= #-Wno-bitwise-op-parentheses -Wno-error -Wno-implicit-function-declaration \
 	-Wno-implicit-int -Wno-int-conversion -Wno-int-to-pointer-cast \
 	-Wno-parentheses -Wno-return-type