Firstly, just so it is absolutely clear, I have absolutely no sympathy for Trump, I think he is despicable, deplorable and any other similar -able you can think of.

Interesting comparison to Cuban missile crisis, and the finer diplomatic points thereof.  But no side actually fired missiles as far as I know which is why this crisis is different from that one.  So what should the USA do if NK sends 4 missiles to Guam as promised?  Consider what the responses should be in three scenarios
1.  missiles are launched, are intercepted or strike off Guam, but are unarmed
2. missiles are launched, are intercepted or strike off Guam, but are "only" armed conventionally
3.  missiles are launched, are intercepted or strike off Guam, and are nuclear armed 

Even if unarmed this is a huge provocation.  And if they are armed, even if non nuclear, this is tantamount to a declaration of war.  And if they are nuclear armed, then its a whole lot worse.