Originally "petrodollar" was just a name for dollars that are used for oil trade, but then someone came up with a theory that all USD value holds on this oil trade, and if countries will switch to other currency, USD will collapse. This theory completely ignore all other international trade conducted in USD, which is far bigger than just oil trade.
That's also a narrative without proper backing, why would US economy collapse if international trade will switch to other currency? Inflation alone can not kill economy, and it's not even clear that the supposed dedolarization will cause massive inflation.
You are correct that the term "petrodollar" was referred to dollars earned from the sale of crude oil in international trade. However, this concept evolved overtime, and now it is widely perceived that US dollar value influenced by demand for oil. Therefore, In case of any shift from dollar to any other currency or basket of currencies, could potentially have significant impact on value the of dollar and US economy.
Inflation is a complex issue and it is influenced by number of factors including devaluation of currency, and it is not yet clear ho dedollarisation will affect US dollar.