This is a very skewed view, to imply that there is a umbilical cord between BTC and USD.
Lemme summarise couple of points to ponder:
1. Although most Bitcoin nodes are in China, the most
BTC speculators are from US.
2. What defines the size of a market is not it's location, but the volume of currency-pairs traded on that market.
3. Mt Gox provides the largest number of markets, the one with the highest volume (by far) is the BTC/USD.
4. There are other smaller exchanges, who also offer the most popular pair, but their volumes are not that great.
5. US citizens form the largest group of BTC/USD speculators, no one stops them from trading any other currency-pair, but they have chosen that it is most convenient for them to trade for BTC/USD, deposit and withdraw in USD too.
6. There are myriad of traditional currency exchanges, some of them very good too (XE Forex comes to mind), but obviously people do not want to be bothered to trade currencies in multiple dimensions
,
example: trade BTC/USD, withdraw in XE wallet in USD, exchange that for EUR, trade EUR/AUD, deposit AUD to MtGox, trade AUD/BTC, profit!7. Liquidity is king, at least in the speculator's land, hence that's what defines a good market.
8. With the blockage of Dwola, MtGox has found themselves with a challenge on their hands, but nothing so severe that they are not able to address (proven history of problem-solving) in time.
9. So, the real challenge is facing the US based speculators - if they want to trade the BTC/USD pair, the onus is on them to find an exchange that offers great liquidity and transaction volume in their choice of fiat, then they have to find efficient way to deposit and withdraw from that exchange.
10. No speculator cares about centralised/decentralised nature of the market, they are quite used to a centralised/regulated exchanges.
11. It takes time to react to any changes in environment, Rome was not build in one day.
Methinks...