Former Republican US Senator Jeff Flake officially became US ambassador to Turkey on Wednesday at a critical time for the NATO allies, after presenting his letter of confidence to President Tayyip Erdogan. A vocal critic of former US President Donald Trump during his 2013-2019 tenure in the Senate, Flake arrived in Ankara earlier this month to succeed David Satterfield, who is now US Special Envoy for the Horn of Africa. He starts the job as NATO members and other Western states mull responses to Russia in the event of military action against Ukraine. Ankara is close to Kyiv and Moscow, has of…