That's a way to bolster it, certainly. None of the listed companies are on the hook for US debt and they'll just relocate if the US becomes a liability. Their value isn't (greatly) at danger of collapse if the debt becomes overwhelming.
There are also healthy ways to encourage economic growth, but those are too boring for the current moment.
The US is the largest market for most US companies, so if consumer buying power is erased (e.g. through a treasury default or inflating our way out of the debt) those companies will drop substantially in value.
Potentially that will be the case in actual terms. Likely that will be the case in terms of their growth rate. But (for most) that certainly won't be the case in relative terms - the large US corporations would ride through such a decline taking an even bigger slice of the global pie.
There are also healthy ways to encourage economic growth, but those are too boring for the current moment.