Bitcoin's resistance to attack is rooted in three properties: its barebones simplicity, the vast processing power that does nothing but ensure the safety of this very simple design, and the distributed nodes which need to achieve consensus on any change for it to take effect. Imagine the digital equivalent of placing the entirety of the U.S. military's infantry and equipment around a school playground to protect it from invasion and you begin to get an idea of how overly fortified Bitcoin is.
