After decades of Cold War spending, the US had to find a way to keep its massive war budgets and domestic spending going without ruining the dollar. Controlling the flow of dollars spent on oil turned out to be a fix.
Private ownership of the means of production is the fundamental institution of the market economy. It is the institution the presence of which characterizes the market economy as such. Where it is absent, there is no question of a market economy.
If oil prices remain at a sustained high due to a war with Iran, it would mean a higher cost of living for most Americans, but it could help certain regions and populations within the US, such as oil-producing states like Texas and Oklahoma.
The Iraqi parliament response to the recent US airstrike — expelling all US troops from Iraq — suggests that an escalation of the ongoing US-Iran conflict would not be as simple as pro-war factions of the US regime would like it to be.