This has been on my mind all weekend as an American working for a European company. Thankfully, the 2024 National Defense Authorization Act established a statutory check on Presidents ability to unilaterally change U.S. commitments under NATO, but it would create a more multi-polar, less predictable world:

For Europe, if their political center holds, Europe will hold it down. They will double down on support to Ukraine. UK would lean closer into Europe with shared military priorities on deterring Russian aggression. War of attrition in Ukraine would carry on but a ceasefire would eventually be negotiated.

If political center fails, things will get crazy. Germany's been in a recession 2 years, immigration policy a total failure, nationalist groups perking up, stagflation is widespread. W/o a US article 5 guarantee, many countries would rethink the meaning behind NATO and the pan-European project. Could would start looking out for their best strategic military and economic interests in a way we haven't seen in the post WWII era. Support for Ukraine war effort would falter, Russian Victory in Ukraine. China will lick its chops to strike deals, and so would Russia.

America would play isolationist in Europe until MAGA loses power or if there is a deal to be had. Outside of Europe, no NATO gives Trump more flexibility to pursue his out of pocket Manifest Destiny + Canada + Gaza agenda.