When he was President, Trump scrapped our free-trade agreement with our two biggest trading partners with no plan; backed out of a Pacific rim trade plan designed to exclude and balance China; damaged our relations with the EU; and launched an incoherent trade war with China with no declared goals.
For context, Yglesias has written detailed threads and articles on his blog about how devastating Trump's proposed economic platform would be to the economy, inflation, and the deficit. This is the response from an NYT economics reporter.
And there's the longer-term outlook (it would help the economy if we restrain climate change, and don't just mindlessly drill oil and mine coal) and Trump setting on fire the US's global role as a destination for international students, who either return home knowing the US or stay here and build.