The Pax Romana lasted 200 years, during which time there was peace and prosperity throughout Europe. The Pax Americana lasted 80 years, during which time there was peace, prosperity, and even democracy throughout Europe and most of the Western World (most of the time, anyway). Under the (somewhat) benevolent guidance from the U.S., there were no major wars among America's allies around the world and trade flourished, to (almost) every country's benefit (especially America's). It was based on mutual respect and cooperation (independent of geography) and a tacit agreement that big countries would not try to bully small countries, even if they could. Soft power and gentle persuasion usually kept everyone on the right path. It wasn't perfect, but it largely worked.
The reason it worked is that smaller countries knew that if they were attacked, they could feel confident that America had their backs. This made them somewhat complacent, but it also deterred aggression from big countries. Russia (pop. 143.8 million) knew that invading Estonia (pop. 1.4 million) meant that it would have to fight off the U.S. (pop. 340.1 million), which had a larger and infinitely more capable army, navy, and air force. Successive Soviet and Russian leaders fully understood that. The American nuclear umbrella also made it unnecessary for smaller countries to develop their own nuclear weapons.
That era is now finished. Gone. Probably for generations, if not forever. Donald Trump hated it, even though it benefited America enormously. Yes, there were some costs for defense and foreign aid, but using soft power, America usually got what it wanted, such as cheap imports that benefited American consumers and export markets for products America produced in such abundance (like food) that the domestic market wasn't big enough to absorb all the production.
The new era might well be one of spheres of influence in which big countries get to dictate their will to their smaller neighbors. Roughly speaking, China gets to dominate Asia, Russia gets to dominate Europe, and America gets to dominate the Western Hemisphere (with a belated thank you to James Monroe). This is something Vladimir Putin surely loves. No doubt he mentioned the idea to Donald Trump, whose ears perked up when he heard it. "Vlad, buddy, you're a genius. Why didn't I think of that? Thank you, thank you."
This new model would explain why Trump wants Canada, Greenland, and the Panama Canal: They are in his sphere of influence and thus rightly his for the taking. It all makes sense if you see the world divided into three mutually exclusive spheres of influence. As long as each of the three dominant countries sticks to its sphere, there will be peace. There are a couple of sticking points, like the Middle East and Africa, but they can be left to their own devices for the most part without disturbing the New Global Order. What happens there is of little concern to the big players.
Many Americans are (initially) going to cheer on this new order—until they eventually realize that they have been handed a monkey's paw. The assumption of peace and access to resources will suddenly be wrong. For example, if China decides to take Taiwan, it will probably succeed if America stays out of it. Then Americans will discover that the 1,000-3,000 semiconductor chips in a car that comprise 40% of the total price of the car have tripled in cost, simply because China wants to destroy the U.S. car industry, which could cripple the U.S. economy. It would take years for Micron Technology and Texas Instruments (which are more focused on small, cheap chips than Intel) to ramp up production to replace Taiwan. In due course, Americans will discover that the world (including America) is a poorer and more dangerous place, but there is no UNDO button. (V)