The surface to air missiles carried by the Nathan James are over 21 times faster than a cruise missile such as the type launched at the National Archives. As such, there would be less than 5 seconds flight time to destroy the cruise missiles, not the almost 20 seconds shown.
When the Chinese forces at the National Archives request fire support from the Hanan the ship fires three cruise missiles. The LAM's used by the Chinese Navy have similar warhead yields to the US Navy's Tomahawk LAM's, making three massive overkill to take out a small ground force. In fact it would be enough to take out the entire complex killing everyone on the grounds, including the Chinese soldiers. Fire support would have been provided by the Hanan's deck gun, just like how the Nathan James uses their five inch gun to give fire support to land teams.
A subsonic cruise missile of the type carried by the Henan would take almost 5 minutes to fly the distance shown to the National Archive, not the slightly over 1 minute time stated by a character.
The land attack cruise missiles used by the Chinese Navy have a similar cruising speed as the Tomahawk LAM's used by the Nathan James, which is Mach 0.7 or 567 mph. The CMS Hanan looked to be about 6 miles from the National Archive, it would take a missile traveling at that speed 0.63 minutes to travel 6 miles; taking into account the missile's acceleration curve an impact time of one minute is quite accurate. A target would have to be a little over 47 miles distant for a cruise missile to take 5 minutes to reach it.
When setting up for the mission, the dive equipment is clearly closed circuit, when they are in the water they are using open circuit equipment.
An army general is wearing the green uniform that was phased out in 2015.
The radar map on the Nathan James shows the National Archives as being around Yokohama, when they are actually in Tokyo, about 16 miles farther away.
The screen captions said the Nathan James was in the East China Sea. The radar screen shown placed it hundreds of miles away in the Sagami Bay.
Slattery says the Henan is patrolling "3 clicks" or 1.8 miles offshore. The location shown later after missiles are launched is about 10 kilometers or 6 miles offshore.
In the shot of Missouri there are mountains in the background more akin to the American Southwest.