And Trump making things like trade, commerce, economic alliances, and international cooperation a massive headache only pushes other frustrated nations to form blocs without the US, and they'll eventually figure out ways of effectively doing business without us. It's already happening in the Pacific, and the EU is rolling its eyes and whispering amongst themselves, as well.
Then again, these conversations and whsiperings are always happening. Countries are not US "allies" because they like it (especially the people in charge of them) - it's because it's rather hard to get around the the US. They don't have anything serious lined up.
Think about the EU - a multi-generation project, heavily disputed, very hard to put together, or even to keep together. And it's not buying its members that
much independence from the US. There's no supercharged EU (let alone a Pacific Union) waiting around the corner, just because the US is being impolite.
Of course, everything is fluid in the long run. A generation of Trumpian US foreign politics might change a lot. But that would clearly not be about the person Trump, it would just make Trump the leading edge of a wave that was coming anyway.
The strength of the US economy has foundations in trade and global geopolitical power.
I am not sure this true. The US surely benefits from them, but it's not the base, it's superstructure
The US is about as close to an autarky as you can find today. In raw numbers: there are only a handful of countries with a lower trade-to-GDP ratio. It has very few strategic imports. While the US could, for example, cut off the fuel supply to the EU, or China, or quite some other countries. Think Suez crisis. Most US exports are extensions of domestic production, not export-first oriented. While many important firms in China, Japan or Germany would collapse without exports.
I would turn this around: US strength in trade and in geopolitics are founded on its domestic economy. The US can engage or disengage with the rest of the world on its own terms, while the rest of the world cannot do so in reverse.