The U.S. is sending experts and fire retardant. European and Mediterranean countries are sending aircraft, which would seem to be more cost effective than sending ours, IMHO. This is only what I’ve been able to find so far.
We have some multi-function C130’s that would have the range to get there. There’s a privately owned DC10 that could also go, and that 747 they’re talking about is from the U.S. but, as you said, the closer assets make more sense. They’re going to have a real challenge avoiding aerial conflicts with the 747. It’s faster than everything else in the air. Turnaround time on it is pretty extensive, too. Most it’ll be useful to pre-treat broad areas.