The D Brief: China’s retaliatory tariffs; ‘Constitutional crisis’ in DC; ‘No improvement’ in F-35 software; Latest natsec nominees; And a bit more.

President Donald Trump’s 25% tariffs on Canada and Mexico have been delayed 30 days, Prime Minister Justin Trudeau in Ottawa announced Monday afternoon, several hours after Mexico’s President Claudia Sheinbaum forged a similar agreement with the White House.  What’s new…sort of: Trudeau agreed to appoint a border security chief and to proceed with a $1.3 billion border plan, which officials in Ottawa had already announced on December 17. The plans call for &ldq