Another history lesson, The United Kingdom of Great Britain and Northern Ireland is four countries rolled into one , Scotland, England. wales and Northern Ireland  are joined together but separated by a common cause that being we usually do not like each other too much

 only kidding we get along fine ever since 1706/1707 although we do a lot of things as one country(military etc etc) a few things were kept separate like Scottish Law and English Law also the education system are also separate as is many more things.
Each country has its own flag as the union Jack is a combination of each flag, so asking why the Saltire or St Andrews cross is not showing is like asking why the Washington State flag is not under your name

 as America is basically one big country with 48 countries inside it.(not counting Alaska/Hawaii)