I think that "bubble" in this context means greatly overvalued, but not necessarily that there is an imminent danger. From the article, seems actually the opposite: the bubble is self-sustaining, because it depresses the other markets and economies and encourages even more do redirect all resources on the US market. Of course at some point things will change, but that point might be far into the future.
That is indeed possible, and generally one has been missing out if not in the US market (I used to sit on derivs/credit/etc desks, though not myself trading), but the near-term risks from likely innumerate, cruel and reckless US policies seem unreasonably high to me. And I have a fairly high risk appetite!
I am not authorised to give financial advice etc etc but I think that it makes sense to have a substantial fraction of assets (but not all) where you live or correlated with its market, especially retirement funds. So I moved mainly from the US to UK for simplicity and speed, but I may push some of that away into non-UK markets when I muster some enthusiasm.
If you are in the US then maybe markets correlated with the US but not the US (Canada?) may be a sensible alternative.
