What are the fundamentals of a strong economy?

Large population...nope look at Russia, Indonesia and China vs Japan, Sweden, Norway and NZ.

Landmass... nope Australia is the size of Europe but it hardly has the same National Power as the EU.

Diplomatic clout... this is probably more a combination of its population (market to sell to like China's potential), military power (USA), cultural similarities (USA+ AUS + UK) (like stick to gether), economics (USA) (if you can buy/sell things they like).

Military... is a raw form of power but does a large military benefit the people as much as other government offices? A large military drains the economy. Look at what happened to USSR and how it effectively lost the cold war because the economy sank.