What better way to hurt the designated enemy and make others bare the cost?

Trump's America First in practice relies on a near-sided and overly simplistic understanding of the world (Win-lose, whatever is benefitting others must be a hinderance to the USA). Hence fighting the tariff wars against allies (Canada, Eu). Hence destroying Nato' credibility that was carefully built for 70 years. Hence ceasing to be Ukraine's ally (but continuing to be a trade partner, that sells weapons as long as Europe is paying). Hence helping Putin. Hence instigating problems with Taiwan if that means that TSMC will move some manufacturing to the USA.

It's a really miopic view, but at least on their part the behavior is intentional (consequences, on the other hand, are surprise for them).