Do not underestimate the dollar. If the world falls down then only gold can become dimensional materials. Bitcoin primarily depends on electricity and the Internet
No one is underestimating the US Dollar. Other currencies such as the Euro and the CNY have been trying to displace the USD as the currency of international trade for quite some time now. But they have failed miserably.
It seems to me that the Americans have nothing to do with bitcoin, but they may prevent the conversion of bitcoin into other currencies. This can significantly reduce the demand for it if it is not established free circulation of bitcoins.
How is it possible to prevent the conversion of BTC to fiat? Even if they close down the exchange sites (which is practically impossible), the conversion will still occur among peer-to-peer networks.