History does not repeat - but it sure can rhyme...
Look at Kaiser Wilhelm... a close relative of both the Russian and British Royal families, and a total nut job.
The British were more concerned with their traditional enemy, the French, rather than the Germans... many British elites had German friends and family...
But Wilhelm had very similar character traits, and attitudes to Trump... and ultimately, he led the world to WWI... and ended up at war with countries that otherwise might have been natural allies.
Now we have Trump, Greenland/Denmark and NATO....
Trumps inclinations would be to ally with Russia (he is far more aligned with Putin, than with the EU!!)... his process of pushing NATO and the EU ever further away from the USA has been an ongoing project.
Now it is likely that NATO will deploy a brigade in Denmark, under Danish control.
This could easily result in a USA vs NATO war.
NATO is Russia's natural opponent - does Russia then use that as an opportunity to attack from the East?
This sort of combination could easily be the spark that lights WWIII.
China's focus on Taiwan, could place it in opposition to the USA - and the Chinese / Russian situation has always been "sensitive" - the Chinese could become NATO allies against Russia and the USA. (this is no stranger than the bedfellows that WWI and then WWI created!)