If you examine a postage stamp from the United Kingdom you will note that the name of the country is missing. This is a commonplace of philately.
Likewise I believe it is a supportable convention to abbreviate topic titles such as Paris, Texas or Saguache County, Colorado or even simply Dorset or Yorkshire. There is a slight objective problem for those who have some English but are not throughly familiar with English language popular culture. Somehow adding USA or England on to the examples seems quite awkward.
The convention for the reader is that if no country is mentioned the United States or Britain can be assumed.
Fred Bauder