Pyongyang routinely condemns the exercises as an example of hostility from the U.S. and its "puppet" in Seoul.
The images celebrate the recent missile tests and condemn the latest round of U.N. sanctions.
South Korea's President Moon Jae-In said the North was inching "closer to the threshold of the red line."
North Korean ruler Kim Jong Un examined plans targeting the U.S. territory but said he was not going to give the order to strike any time soon.
The Korean Children's Union, which enlists children between 7 and 13, pledged its readiness to take up arms.
Kim said he would "watch a little more the foolish and stupid conduct of the Yankees."
Kim Jong Un's 14-day absence from public appearances ahead of the celebrations may signal preparation for an at-sea SLBM test.
The ANZUS Treaty was first invoked in the aftermath of the 9/11 attacks, and could be invoked again.
China has a mutual defense pact with North Korea that legally obliges it to come to its ally's aid.
Asked about Trump's latest comments, Secretary of Defense Jim Mattis instead emphasized the importance of diplomatic efforts.
President Trump's warning about meeting North Korea's belligerent threats with "fire and fury" sparked criticism at home and abroad.
The White House didn't have a clear answer as to whether the president was advised on his fiery North Korea remarks.
A Canadian delegation arrived in Pyongyang on Tuesday to discuss pastor Hyeon Soo Lim's release.
North Korea's threat came as President Donald Trump warned Pyongyang would face "fire and fury" if it kept up hostilities.
The new round of U.N.-mandated sanctions target vital sectors for the North Korean economy.
The U.S. announced the ban on its citizens traveling to North Korea in July and published it on the federal register on August 2.
Pyongyang should be shown the cost of pursuing nuclear weapons development, a State Department official said.
The U.S. travel ban to North Korea will enter into effect on September 1.
Army Chief of Staff General Mark Milley warned, however, that war in the Korean peninsula would be "highly deadly" and "horrific".
By the time the war ended, nearly 1.8 million Americans fought in the conflict, nearly 37,000 soldiers died and more than 7,800 remain unaccounted for to this day.