The Great Seal of the United States features an eagle holding a sheaf of arrows and a bunch of olive branches in its two talons. These two objects symbolize US preparedness for both war and peace, but, as the eagle's head is turned toward the olive branches, this implies Amercia prefers peace.
For example, when US Presidents Bill Clinton, George W. Bush and Barack Obama announced military operations in various foreign nations, the flag was folded so that only arrows, the symbol of war, was visible. For non-military announcements, the flag is folded so that the olive branches, the symbol of peace, are visible.
But something was different with Trump's use of the flag this time.
When Trump announced the strike on Syria on April 14, the flag was folded so that the olive branches were clearly visible. While the arrows were also visible, they were covered with tassels and one must look closely at the corner of the screen to see them.
Some Twitter users noticed this and speculated this might be a signal that Trump does not really mean business.
Interestingly, there have been occasions in which the flag was folded so that only arrows are visible, but these had nothing to do with Syria. For example, this video when POTUS speaks about how he is going to secure the US borders and impose the rule of law on the United States.
The Great Seal also sparked some Twitter controversy in 2017 when media reported that the Presidential Challenge Coin has been given a makeover. The new design reportedly replaced the national motto and the Great Seal with Trump's "Make America Great Again" motto; the eagle on the new design was also facing toward the arrows.