However, I am talking very large scale here, not minor increases in efficiency which are part of the normal economic growth of any country. Given enough time (think decades and decades) the actual goods and services rendered (lets just call it product) will outweigh currency in terms of it's effectiveness in the global economy, since ultimately papermoney has relative value to product only, and product has value in itself, money or no money. Money is just a medium.
Look at it the way a lot of people do (currency value only) and you have a strange conundrum to explain... if the US is in such dire financial straights, how come it largely operates the same way it does in the last 2 decades apart from a minor inflation? Because our product have not changed drastically. The US still has a very strong economy, it just owes a lot of collateral and somehow manages to use more than it makes. The US economy (like it's citizens) need to trim the fat... not a coincidence! I am not saying this means working more, it's a combination of efficiency increase (as you aptly pointed out) as well as reduction in unjustifiable and wasteful luxuries like $2,000 toilets in the Pentagon.
And how come the Chinese economy is a threat... what makes China so special? Their MASSIVE product... they just haven't figured out the infrastructure required to compete in the currency market until the last decade.
On the flipside, look at the Russian economy. Still totally destitute... I think they will recover, but it might take 20-30 years and it will probably depend entirely on their ability to develop those resources they're still sitting on, and THAT will probably only be driven by the inevitable development of the technologies used to harvest them as well as the global desire for those resources as a launching point for recovery. This is a far fetched prediction of course but you get my point that these things take a long time to see the effects. Product > currency. Right now Russia has very little in the cards for it's recovery except natural resources, which as I said only offset so much, something which is very apparent with Russia--massive natural resources yet they're still stuck.