The biggest damage is the souring of relations with other countries, who now no longer see the US as a reliable business partner. They have nudged countries in the EU to rather look to China. The longer Trump is in office, the bigger the damage gets. The long term course might already be set away from the US and towards China. The loss for the US cannot even be estimated yet.

Also the US is working hard on losing their military dominance. Engaging in unnecessary wars, offending its allies left and right, who are now starting to invest more into their own military, since they have learned, that they cannot rely on the US any longer, while China plays the catch-up game and is getting closer to US military capability every year.

Reputational damage is enormous of course and the US hands China easy PR wins after wins.

This seems to be the current trend. Projecting this into the future, it seems likely, that in 10, 20, 30 years from now, the most powerful global player might be China, instead of the US. Obviously, in decades a lot can happen. Future US administrations however have got a lot of repair work cut out for them. How can they convince international partners, that this does not repeat in the future, the next time a crazy administration is elected? Can they at all? Or can they fix the political landscape in their own country in that timespan? It kinda looks like their are stuck.