I have some issues with this premiss:
"The stock market is up, unemployment is down and the economy seems to be picking up some steam. The streets are mostly safe, the nation is mostly secure and the world is mostly at peace."
But, yes, similar could have been asked of Bill Clinton. If he was otherwise a good President, does it matter if he was a sexual predator?
However, the US risks being under the direct influence of a foreign power that has been an adversary at best.
The US risks the President putting his personal wealth ahead of state interests.
The US risks nuclear war because the President can't do diplomacy and can't keep his mouth shut.
All of them quite relevant to the country, regardless of the stock market.