Greenland - a geopolitical space on the global chess board?

[axj]

Can I check something - does the US president have the constitutional power to add a new state to the US?

No, the president needs the congress for that. Also, Greenland would most likely be a territory like Puerto Rico, not a state.

I had a similar thought recently, why now? Why the US is meddling with the internal politics in Venezuela, why are they looking at Greenland as the future 51st US state? Is it for geopolitical reasons only, due to the inevitable uprising of a multipolar world?

It seems to be mostly that, as well as probably Trump's ego. In some ways it is better that the US accepts the multipolar world and focuses on being mostly a regional power in the Americas. Though it may not be that great of a deal for Latin America, depending on how the US will manage its sphere of influence.