This indicates that the letter is genuine, and also shows that people from varying walks of life are following events in the country concerned. If you have any special interest or link with the country, it is a good idea to mention this in your letter. For instance, you may have visited it, studied its history, or been a member of a local association for friendship with it. A simple, one line letter is adequate and is certainly better than no letter at all. A good rule is not to write more than one page.
Long letters are less likely to be read.
Only in exceptional cases are long letters effective.