Turkey is an important US ally by saying that they should be part of the EU he’s playing to their position and helping keep them on our side. Of course he knows full well that France, Germany and an number of other EU countries will never allow Turkey into the EU.
The Turkish economy doesn’t meet the requirements for admission and they already have a problem with Muslim population growth in Europe. If they let Turkey into the EU they lose control of their boarders and workforces. Also Turkey’s boarders are totally porous to Islamic terrorists giving them a superhighway into the heart of the EU.
This is true. Besides Turkey (like some EU members) is adamantly opposed to any acknowledgment of Europe’s Christian heritage being included in the EU Constitution.