That means the American plane took off from a carrier (George HW Bush), flew over all of Russia's radar and missile sites in western Syria, shot down the Syrian Su-22 in Raqqa, and then flew right back over all the Russian anti-air sites.
The reason Americans could do so without any worries is because having announced the flight to the Russians through the deconfliction channel (but not their intention to be shooting down Syrian jets without trying to contact the Russians again) the Russians were honor-bound to not molest the US plane.
You can understand then why Moscow might feel particularly furious today. The US made Russia look weak though its F/A-18 fighter was actually at the mercy of Russian air defenses for its entire foray into Syria and back.
This does not mean a whole lot for US aircraft which operate from Turkey's Incirlik airbase, and the new US airbase in Kurdish-held northern Syria. Taking off from their eastern bases they have little reason to be crossing the Euphrates, and that's even true if they're targeting Syrian jets which they can do from hundreds of kilometers away.
The US carrier-based aircraft however, are an entirely different story. Their life just got a lot more complicated. If they want to join the fray in eastern Syria they now have to fly over Russian anti-air sites which will be tracking them as targets the whole way. Is the US Navy willing to put its pilots in that sort of situation?
The alternative is for USS Bush to sail further north and have its aircraft reach eastern Syria via Turkish airspace, but that would take the consent of, and increase the reliance on, Turkey. Seeing that Ankara is already downright hostile to the forces US is backing in eastern Syria that might not be sustainable and stable option either -- or may come at a high political price.