Today is both the Feast of the Annunciation (on the New Calendar), and Greek Independence Day. With that in mind, I decided to look in my archives for American accounts of the Greek War of Independence, in 1821. I have quite a few reports from various newspapers and journals, and the single event that received the most attention seems to have been the martyrdom of Patriarch Gregory V of Constantinople. This took place at the very outset of the Greek Revolution, and was a direct Turkish response to the initial rebellion.
Patriarch Gregory was murdered on Pascha, in April, but the news didn't start to trickle into the United States until the summer. Here's the first report I've found, from the Connecticut Gazette (7/11/1821): “Constantinople is a scene of disturbance and massacre. The grand Seignor, to revenge the insurrection in his northern provinces, has had recourse to the most dreadful reprisals. The Greek Patriarch has been strangled, and four Archbishops have been massacred.”