The US dollar value like all fiat is based on the belief of the people holding it. Once that belief crumbles in anyway it can come tumbling down very quickly.

Honestly there is no difference with the value of BTC, or any crypto, as it's all about consumer confidence in the coin. Without it the value will fall. Right now people are not confident that the government won't cripple the crypto markets and that is why we are seeing the pullback.