EU? Economic, yes: it's indeed as large (in fact, larger) than the US. Military, not really: US outspends all of its close allies combined. Diplomatic: they're so fragmented they can't get anything done.

China? Economic, hardly: it's getting there, but it's entirely dependent on the US consuming its output. Military: they're outgunned 6:1 by the US alone in terms of spending. Diplomatic: not the slightest bit, except on its immediate neighbors (and in Africa, to an extent, if you count showering local strong men with cash as influence).

The EU is fragmented right now. We still don't have a unified European government (state are still somewhat sovereign). We still don't have a unified international representation. And we still don't have a unified army.