The immediate consequences for Turkey’s purchase of the S-400’s was exclusion from the F-35 program.
Turkey has however continued to upset both the US, NATO, France, Germany and Greece in various ways.
There was a threat of having CAATSA slapped on them by the US if Turkey/Erdogan did not alter his stance. Erdogan it appears seems to have ignored this in much the same way he previously decided that he could ignore the F-35’s being withheld.
It has taken a while however it has finally happened. The press statement below was yesterday 14 Dec 2020
Today, the United States is imposing sanctions on the Republic of Turkey’s Presidency of Defense Industries (SSB) pursuant to Section 231 of the Countering America’s Adversaries Through Sanctions Act (CAATSA) for knowingly engaging in a significant transaction with Rosoboronexport, Russia’s main...
www.state.gov
The Secretary of State, in consultation with the Secretary of Treasury, has selected the following sanctions from CAATSA Section 235, as implemented by Executive Order (E.O.) 13849, to impose on SSB:
a prohibition on granting specific U.S. export licenses and authorizations for any goods or technology transferred to SSB (Section 235(a)(2));
a prohibition on loans or credits by U.S. financial institutions to SSB totaling more than $10 million in any 12-month period (Section 235(a)(3));
a ban on U.S. Export-Import Bank assistance for exports to SSB (Section 235(a)(1));
a requirement for the United States to oppose loans benefitting SSB by international financial institutions (Section 235(a)(4)); and
imposition of full blocking sanctions and visa restrictions (Section 235(a)(7), (

, (9), (11), and (12)) on Dr. Ismail Demir, president of SSB; Faruk Yigit, SSB’s vice president; Serhat Gencoglu, Head of SSB’s Department of Air Defense and Space; and Mustafa Alper Deniz, Program Manager for SSB’s Regional Air Defense Systems Directorate.
The sanctions will affect roughly 40% of Turkey’s defence imports from the United States and could have a very big effect should they continue for two or three years. Air force equipment and land systems are most vulnerable.
For the air force, critical areas the modernisation and maintenance of its F-16’s. The TF-X future fighter project and Turkey’s reliance on aircraft engines. On Army systems, the operational efficiency of radars, command-control systems and armoured vehicles.
Other National projects Turkey is involved with include the T70 general-purpose helicopter, the TF-X combat aircraft, the HurJet training aircraft, the MILGEM combat ship and the export of the T129 attack helicopters.
With his buddy Trump leaving and Biden with negative views on him little comfort there.
Donald Trump’s lackadaisical approach to Turkey's President Recep Erdoğan gave him an opening for an aggressive and revisionist set of policies that pushed the boundaries of Turkey’s relations with America and Europe, writes Henri J Barkey.
www.euractiv.com
Merkle mentioned discussing possible sanctions on EU weapon and system exports,
Chancellor Angela Merkel wants ‘determined course of action’ on whether to end or suspend membership talks.
www.politico.eu
France is already providing Greece with Rafales and other weapons in a clear message from Macron.
France has condemned Turkish President Recep Tayyip Erdogan over comments he made about Emmanuel Macron's mental health and treatment of Muslims.
edition.cnn.com
Erdogan has alienated a number of ‘allies’, obviously feeling that Turkey is capable of going it alone.
He may soon however find that he has slightly overestimated this concept, and that his neck has possibly extended a little too far for real comfort.