I don’t think things would go that far. Look what happened with the tariffs earlier in the year, he had to reduce them to a large extent when it looked like there were going to be issues with the US government bond (treasuries) market. The so called “bond vigilantes” had a quiet word with him and he was forced to scale them back.
Inflation is a killer for fixed interest bonds and would not be allowed to get that far out of control as too many rich and powerful people would have too much to lose.
In terms of your investments, then your equity portion should just be in a global tracker (which currently is made up of around 60% S&P 500). The proportion in equities vs cash/bonds will depend on your current circumstances and your risk appetite.
Shares are often considered to be too high, but if you cash out and sit on the sidelines then you could lose out as they continue to rise or stay at current levels. Also, if you did decide to sell up, then the difficult part is knowing at what level you buy back in. Say the market fell 20%, would you then buy back in, or would you think that things were going to get worse and hold off until that happens (or may never happen), and you then may be perpetually stuck on the sidelines waiting for things to crash further, and not sure whether to stick or twist.
It’s impossible to time the market, so just ensure you have a cash buffer to cover your expenses for at least 6 months if you are still working, or several years if you are retired. That way, if there was a crash you don’t have to sell shares at a depressed value and can wait until they recover.