My impression from an outside-in view as a European substantially invested in the US, but without any claim to deeper insight or expertise: The relative good performance may be based on comparative factors (such as likelihood to pull through or successfully shaping the economic "landing") and on lack of (better) alternatives.
The US may throw billions or trillions into economic recovery, but so do the EU or China. Maybe the US citizens will be individually hit harder (financially) than their more cushioned European counterparts -which really sucks on a personal level. However, they may also bounce back faster (than others) based on less centralized decision-making and a stronger entrepreneurial culture in the US.
The thing is, no one knows. There is no clear evidence (yet) that the overall trade and production structures are irrevocably changed. Maybe the US is getting more sclerotic, but in Europe, the trend seems to move into ever more risk-averse directions, too. So, while economically things look bad, they seem to look pretty bad everywhere. The Dow may be a headless chicken. Or investors just don't see better alternatives. Just guessing, ofc.