The Welsh were as much a part of Empire as the rest of Britain.
Twice?
The US won roughly twice as many medals as the UK and has roughly five times the population, so really the US underperformed.And also because we easily put the UK and everyone else to shame when it comes to the number of medals we won, and you don't see us trying to rub it in everyone else's faces.
But you have nothing to ashamed about, India (population 1.2 billion) only won two medals, even Bulgaria (populated by gypsies and people working in the sex industry) won more medals than them.