Ankara’s worsening relations with Washington and European capitals over a host of issues have led to more pressure on Greece: a sharp increase of immigrants and refugees crossing from Turkey in recent months, the ongoing detention in Turkey of two Greek soldiers who strayed across the border in early March and a series of confrontational military actions by Turkey. These all highlight the dangers that Greece faces as the European Union’s frontier state in a turbulent region.

Mr. Erdogan presents himself as the victim of an attempted coup, allegedly by a United States-based former ally, Fethullah Gulen, and as the champion of Muslims everywhere, including the Palestinians. Lately, in the region’s fluid network of rivalries and alliances, Turkey, a NATO member, has cultivated closer ties with Russia and Iran while chafing against American constraints on its occupation of part of northern Syria. The drawing of battle lines over Mr. Trump’s recent actions could lead to greater tension among Turkey, the United States and Israel.

Meanwhile, Greece’s relations with the United States and Israel have never been better. The U.S. ambassador to Greece, Geoffrey Pyatt, refers to the country as a pillar of stability in the region and U.S. officials make use of important air and naval facilities at the Souda Bay military base on Crete. The leaders of Greece, Cyprus and Israel held their latest trilateral meeting just last week, focusing on energy issues. Greece’s increased strategic value could work in its favor, as the country seeks American and European backing to keep Turkey in check and to help its own economic revival. However, the more Washington and Brussels lose leverage with Ankara, and the more unilaterally Turkey acts, the greater the risks for Athens.

For Prime Minister Alexis Tsipras, whose radical left-wing Syriza party is in a coalition with the far-right nationalist Independent Greeks, closer relations with the United States and Israel at this time could also create domestic complications. If the United States and Israel become embroiled in further bloodshed, such as that which attended the opening ceremony of the American Embassy in Jerusalem, the government will not want to appear too close to them. Several leftist groups are keen to prove they have greater “anti-imperialist” credentials than Syriza. Last month, after the United States, Britain and France carried out missile strikes against Syria in response to the regime’s alleged use of chemical weapons, Communist Party demonstrators in Athens tried to pull down a statue of Harry Truman.

Even more ominous than the tension with Turkey is the possibility that Mr. Trump’s policy on Iran and Israel could drive a wedge between the United States and the European Union, especially if American officials carry out their threat to impose sanctions against European companies doing business with Tehran.