From what I can see, Trump is desperately calling for the support of other NATO allies in the war because the cost of maintaining this war is going ever the initial budget by greater amounts, I don't think he forsaw the Strait of Hormuz blocked as a strategy Iran would deploy and and it's really putting him under serious pressure at the moment.
The Guardian reported last week that the US spent about $2bn each day in munitions at the beginning of the conflict before spending fell to $1bn each day. The cost per day is expected to fall further as the war continues, unless the situation escalates.
SourceThe war cost over $11.3Bn in the first six days and as situations are escalating in the Persian Gulf, Trump knows it would cost the US more to stabilize that area which is why he's calling NATO allies for help, same allies he constantly insulted in the past, he'll learn the hard way if they don't respond.
Iran is strategically extending this war knowing fully well that it would cost the US more to fight the war for a longer duration and this is the case as at now, and it's a major weapon against the aggression of the US. I don't think the US can afford to continue this campaign with high intensity for much longer.