You are forgetting that Russia is an
energy superpower, if you live in Europe no doubt you would of heard on the News, about Russia demanding Higher prices to countries like Georgia (they were low before due to vassalship, but then they stopped being vassals.. i dont know how considering they dont have 50% land or population

)
But Russia has used its leverage before with oil, as it supplies Europe, infact if Russia stopped sending Oil to Europe, that would be a major crisis and infact cripple Europe/ The European Union untill they could secure new deals with the OPEC Nations (stands for oil someing something

) the only other Energy superpower is Saudia Arabia, and well America basicly has them as a vassal, and one potential Energy superpower Venezuela, who actually have more oil then the whole middle east, but in a harder form to extract, which costs more ect.. but as the price of oil rises, Venezuela will be a Energy Superpower.
Another poster talked about USA economy in foreign reserves, and that is entirely true, China and many many other countries have huge reserves of American Dollars, which the American economy may well depend on.. im not sure im not starting Economics in College till a weeks time

, most of this is because of Oil, since you buy the barrel in dollars, its priced that way.. well countries such as Iraq(before it got vassalized by America, and before George W Bush gave speach about Axis of evil and whatnot) wanted to stop trading oil in Dollars but in Euros, then America invaded!! OMGosh Conspiracy!!
Iran is considering the same i think,
North Korea is following suite!
Venezuela is embracing selling Oil in Euros instead of dollars, wait a minute arnt Iran, and North Korea, aswell as Iraq who first thought about selling Oil in Euro instead of Dollar are all of George W Bush axis of evil!! Conspiracy!
Venezuela has been accused of Terrorism aswell, and i think was added to the list and taken off a week later.. tut tut America.. well because of Mainly Venezuela all OPEC nations are considering it, selling oil in Euros, meaning maybe 75% of American Foreign reserves could potentially be sold away, maybe making something comparable to the Wall street crash, if this is not true i wonder why Bush keeps Declaring war/accusing terrorism on all the Countries who are trying to push this through.
China, in 50 years will have stronger Economy then America if current annual growth stays the same, which i doubt.. considering all the Crisis America is in right now Housing crisis which will reappear soon, since they did not fix it, just avert it i say.. Foreign Reserves crisis.. other crisis that i dont know about

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India will have stronger Economy with about 75 years, mainly because China can easily move a town of 100,000 people to build a road easily, because they care about the Nation as a whole and Economic growth, and well India is Democratic meaning it cant get away with such things

, and India needs to sort out its current system, because im not lying its Running the Caste System, it needs to stop doing that( it is currently trying) but well its hard when you have 1-1.3billion people i forget..
Someone wrote about China's power projection and they are completely right, China can only project power within its Region, it does not have a Blue water navy (one like Britain, India or America) which can project itself around the world and invade anywhere, like America did to Iraq for instance.. China would not be able/have a very hard time doing so.. China since the 90s after the First Gulf war, where they watched a side (Iraq again) get beaten, and well China has similar levels of tech when it came to Military, so since then they have been mass updating their military, and are working with Russia to develop / steal new stuff and have a 1st rate military, Also forging closer Links with India, i think within the last 6 months they reopened borders with India, after it had been shut a long time due to a Minor Border war.. China was Friendly with Pakistan, so they got -4 You traded with our worst Enemies with India, and well India was best friends with Russia during the Sino-Soviet split so the same to them, but well soon maybe they will help each other with military tech i bet, Also America sells weapons to Israel, Israel sells it to China, Directly or through India/Russia, China recently tested its anti Satalite weapons, which was a success, which would potentially mean taking away America's biggest Advantage, think of the 1st Gulf war again when they beat (i know again Iraq) Satalite gave them clear picture, it helped take out their communication and infrastructure, so well China is getting there fast...