It will also signal to the world that America is no longer world police, which means the Middle East, Japan and Taiwan will once again come under threat. The Middle East already foresaw this, which is why Saudi Arabia, Turkey and Pakistan are building a regional nuclear-enabled alliance, with open invitation to the other oil economies. Taiwan is most likely to get caught with their pants down, given the lack of US military support.
Interestingly, with the exist of the US from NATO, the largest military in NATO will be Turkey's, that country that Europe has long considered the unwanted bastard child.
https://www.independent.co.uk/news/world/europe/greenland-tr...
Europe only needs to encircle and starve them, not fight them.
With what navy and air force?
A world war meaning... the death of many / most Americans? That's quite the fantasy there.