Accounts on social media circulated a post attributing to American media outlets the statement that the perpetrators of the attack on the Karak church in Jordan were of Syrian and Palestinian nationality, with the participation of an extremist Jordanian cleric.

American media did not specify the nationalities of the attack's perpetrators, and Jordanian media did not confirm them.
The Jordanian Ministry of Interior had published the details of a joint press conference held by Interior Minister Mazen Al-Faraya and Public Security Director Major General Obaidallah Al-Maaytah, convened at the Karak governorate headquarters to set out the details of the security incident relating to the terrorist attack on the Greek Orthodox church in the village of Hmoud in Karak governorate, in which Al-Faraya said that what happened was a terrorist operation carried out by a group of extremists.

Why is this claim misleading?
Information attributed to media outlets that did not publish it: Attributing the identification of the attackers' nationalities to "American media outlets" lends the claim a media backing that does not exist, while American media did not specify those nationalities and Jordanian media did not confirm them.