[Mitchell]

Your most likely nominees?

Likely candidates: Saudi Arabia, Pakistan, Iraq, Iran, North Korea, China, Syria. (I've omitted Afghanistan since I don't think that Sen. Graham would have expressed surprise at that.)

[Allan]

"...if the infrastructure of a foreign government assisting terrorists still exists"

It seems highly unlikely
that Iraq or North Korea or Syria would have an infrastructure
assisting terrorists in the USA.

(Does Iraq even have an ambassador in the USA?)

However,
it is well known that Saudia Arabia has an infrastructure
extending right into the highest levels of the State Department.

Pakistan's infrastructure is not negligible either.
Remember Clinton's old apologist Lanny Davis
is a paid lobbyist for the Pakistanis.