Not quite as small. Combined EU has the largest economy in the world, is by far the wealthiest region on the planet, possesses a huge & advanced military force and despite decline still has pretty substantial manufacturing capacity. (only reason US tops these rankings is because in EU each metric is tracked separately for each country).

So if EU got its shit together and formulated a coherent unified foreign policy - it would be at the very least on equal terms with both US and China. Hence why everyone (from Putin, to China to even our allies the US) are so invested in breaking EU apart (and even succeeding - the Brexit).