After WW2, the US moved to establish a new world order that wouldn't produce world war after the world war. The UN, Marshall Plan, free trade, alliances, and foreign assistance replaced tariff wars and strong arming the weak. The result was 80 years of relative peace and an immense increase in wealth with the US at the top. Trump seems intent on returning to the pre-WW2 world. Major powers call the shots, taffies are used to extort concessions, and weak countries pay the price. Who in Europe would now believe that the US would now protect a small NATO country attacked by Russia?
The trigger for Putin's initial incursion into Ukraine was the possibility of its joining the EU which would have established a more vibrant alternative to the Putin regime next door. Putin wants to be surrounded by similar autocratic states, not growing, free democracies that make Russia look bad. Ukraine is the outlier, so it's hard to believe he will agree to Ukraine joining the EU, NATO or anything in that direction. He wants a vessal state, and Trump is sympathetic with the view. Plus Trump hates Z going back years.
This return means that the US has to attack its allies and friends first. Trump has initially focused on Canada, Mexico and Europe, our closest allies, because they are also our biggest trading partners and have the most to give up. Russia has basically nothing to offer the US. Japan, China, and the Pacific TBD. Trump can use US power to extort concessions, but the result will be the same as Trump's business dealings; a legacy of destroyed relationships and victims.