Turkey, like many of the countries in the region, always seem to go back and forth between Russia and the United States when they want something. Turkey was in an agreement with Russia to the tune of 100 Billion dollars but that had been put on hold after the downing of the Russian jet. Erdogan needs cash and he needs a savior and Putin is the man.
Putin contacted Erdogan after the coup and that simple call allowed Erdogan to save face, a little. He still looks like he's begging Putin for forgiveness. Erdogan is weak and needs Putin's backing in the years to come if he wants to stay in power.
Should the United States be worried about these talks? Yes they should up to a point. Erdogan still has ties to the West, and he needs them. So, he is not going to be stupid enough to get into bed with Putin so to speak, but they'll make out just a little.
The United States should take these talks seriously as we need Turkey in our fight against ISIS. We need their air bases to launch air strikes against the Islamic State. This is an interesting day for all involved. Turkey needs to make sure that it knows what it's doing. If it were to lose the West and only have Russia then Turkey would be at its mercy of Putin.