It is indeed a worry to saturate a trade area with too many events, but the US is large enough, and our federal arrangement is still functional enough, such that certain states can remain economically strong in the event of a double dip recession, Texas in particular.
The US is also one of the 4 powerhouse nations who have a plethora of international motorcycle rider championships (Australia, Britain, and Italy are the others) so it is in Dorna's best interest to maintain US enthusiasm for motorcycle racing. Furthemore, within the United States, Texas and California are powerhouses for developing riders, but who could possibly leave out the Northeast by canceling the Indianapolis round which is the closest FIM homologated track?
Imo, there are many factors at play. Unlike the blatant favoritism for a slumping home market, Dorna's three GPs in the United States are hardly worrisome considering they are the only GPs in all of the Americas, and each event is more than 1,000 miles from another US event. Indy to Monterey is roughly the same distance as Sydney to Perth, and the Indy and Laguna rounds satisfy completely different demographics.
Australia should not lose it's GP, nor do I think it is in danger of happening. If cancellations are necessary to start new rounds, I suspect Dorna will start in Iberia. If Australia loses its round it will happen b/c Oz only has one FIM-legal circuit (AFAIK) which means Dorna has no negotiating leverage.