USA invaded Iraq for petrodollars as Iraq was trying to sell oil in non-dollars. So, USA indeed had a plan. But regarding war with Taiwan, unlike Iraq, once China takes out the government of Taiwan, it will not be a long occupation as Taiwanese are ethnic Chinese and will simply merge into a greater China.
As for European & American sanctions, China supplies most of the manufactured goods to these countries. If anything, they will become poor and lose out. China's production power is more than EU+USA combined. It will simply be a repeat of Iron curtain of cold war but with China having upper hand.