It's kind of old, now, but did you notice something odd on that letter about the trip to Afghanistan? (Colbert did)
"Madame" Speaker?
It's even on the actual letter, by the White House, not DJT's Twitter.
On purpose?
Does he only know "madames"? 
Confused Nancy with Madame Macron?
I have to say that I actually agree with him, that they shouldn't be making such trips at this time, unless there was a very strong reason.
OTOH, I think the SS should shut down to minimum services, lock up the WH for safety and only allow Mueller in. Or just let the crowds in.