> The ruling came from the federal district court for Oregon. As such, it's only binding for the district.
No, trial court rulings aren’t binding precedent even on the same trial court.
> If a federal court in another district comes to a different conclusion, then an appeal to the circuit court might happen
Appeal to circuit courts from district court are a matter of right, a split between districts is immaterial not only as to whether such an appeal is filed but also to whether it is heard.
> Michigan and Oregon are in different appellate circuits (6th and 9th, respectively) so if there were different rulings in each circuit, and an appeal to the Supreme Court succeeds and the court rules, only then does the ruling become binding across all states an jurisdictions.
At this level, a circuit split is traditionally a factor which weighs in favor of the Supreme Court hearing an appeal (as its appellate jurisdiction is generally discretionary), but it is neither in itself either necessary or sufficient. But, yes, it is only when the Supreme Court rules that precedent is universally binding rather than persuasive.
> For now, the ruling is only binding in the District of Oregon
No, for now it is only binding between the parties to the earlier case (and only as regards the specific facts of that case), under the principle of res judicata rather than stare decisis which makes decisions binding on particular (or all) courts.