Hrm, uh, I’ve got one that is already actually happening:

What if many large international seaborne shipping companies announced they would no longer be sending their vessels through the Suez Canal, and this trend didn’t really start spreading amongst the shipping firms until a couple ships got boarded, hijacked, and shot by missiles?

And then what if /also, simultaneously/, Climate Change and other problems caused significant operational problems with the Panama Canal, causing it to allow considerably less shipping volume through?

That would probably cause massive delays in all kinds of raw goods, finished goods and goods in every stage of production arriving all over the world, leading to an amplifying negative cycle of increased shipping costs being ultimately thrown at the consumer, as well as causing serious stress and layoffs and many business closures for smaller businesses either reliant on imports for manufacture or retailers selling finishes goods.

That could even spiral so badly that when combined with other economic factors it could cause a general downturn in the stock market, but even if that doesnt manifest, the generally weakening and worsening economic conditions of the working class would make Biden significantly less popular, right as the election cycle is kicking into high gear.

(The Suez Canal and Panama Canal situations are currently happening basically as I described, btw)