My mistake in conflating the two. Updated - Thanks for pointing out the distinction.
Though donating to it isn't a substitute for donations to the American Red Cross for disaster relief purposes. The ICRC specifically deals with armed conflict.
For disaster relief you'll have to find another reputable charity.
This is not true. The Red Cross in my country, which is an ICRC affiliate, does provide disaster relief. As far as I can tell, this is true across the board.
Eg:
https://www.redcross.org.au/news-and-media/news/australian-b...
https://reliefweb.int/report/viet-nam/thai-red-cross-society...
FTFY. The Red Cross is a reputable organisation that does wonderful work across the developing world. The American Red Cross is the corrupt one.