

Europe would not be able to help much even with greenland under control. The US navy is much stronger and a lot of Europe’s navy is tailored for coastal defense.
The reason why I think he would not invade canada (or greenland) is that NATO would effectively dissolve which would be good for China.
It looked easy but It’s ludicrously difficult to do. Russia tried something similar in Ukraine and got bogged down in a war they still have not got out of.
The fact that it worked and did not turn into another black hawk down scenario is like you say months of preparing, someone on the inside high enough to have information and dislike Maduro enough and a good batch of luck.