What's the alternative and why is it up to us?
Last I looked, Germany, France and Italy had the most to lose from another major conflict in and around Syria. It hardly matters to us at all in the most selfish sense, but it's a pretty big deal to them. Syria is also a lot closer to them so logistical support for any intervention would be way easier for them. If Turkey goes in with, say, 50,000 or 100,000 troops, you're going to have to send in a comparable number and then supply those units.
If we're dealing with truculent Turks, the whole affair could last a long, long time. After all, Turkish supply lines are quite direct, so supporting their army in the field isn't nearly as complicated. I get that the Kurds helped us and are fine fellows and all, but why is it up to us to defend them?
And then there's Congress. They're all up in arms about Trump's proposed withdrawal of forces, but are they willing to declare war? If so, on whom? Without bipartisan support for a major engagement, who's left holding the bag for taking on several Turkish divisions in Syria?
Finally, Turkey is a member of NATO. Exactly what is the appropriate response when opposing an "ally?" NATO is a big organization with lots of voting members. What do the rest of them have to say about this?
I've seen a lot of gnashing of teeth and finger-pointing on Twitter, but no one is discussing the EU Army, such as there is of it. It seems to me like this is their ballgame, not ours. Besides, aren't the Euros flush with cash because they do such a good job with free college and free healthcare and stuff? This ought to be a slam dunk for them.
Or maybe not.