This is my personal assessment: The USA has a moderately large population, and it is the world's largest economy because of that. As a result, the USA is a superpower.
No other countries in the West have this potential except Canada. Coz, other countries don't have enough land space to accommodate a large population and keep the density comfortable for its inhabitants. Australia has a huge landmass, but it is mostly an arid desert and uninhabitable as a result.
The following map shows the comparative density of the population of Canada and the USA:
It seems that most of Canada is empty.
I see that their population growth is big. But, this is not enough to make them a Great power (e.g. UK, France, Japan) or a superpower.
Why doesn't Canada try to make its population grow up to the size of the USA?
