The petrodollar is severely overrated by people who claim it's the cause for every foreign policy decision they disagree with. USD is attractive because the US government is stable and US companies are attractive investments, due to a historical track record of competence and rule of law adherence - unlike, say, Saudi currency, or Russian currency, or Chinese currency. The US government doesn't do a lot of currency manipulation relative to those other countries either.

Of course, that historical record is being shat upon currently, and the importance of petroleum is on a downward trajectory from here on.