Just doing some checking - the US tried as well, but had the same basic problem. NOAA in Honolulu identified the fact there was a tsunami about the same time we did - but basically didn't have anyone to contact in the countries that were most at risk.
There is a failure here, and that needs to be addressed - but the failure wasn't with the identification of the problem in western nations - the failure was that there doesn't seem to be any central contact point in most of the south east Asian nations. You can only issue a warning if you know who to warn.
Whether it would have done much good is an open question as well.
I guess they do not have telephones in that part of the world. Telecommunications have been available for over 100 years.