Every President is a threat. This one is also a bit of a ****. Again, hardly new territory.
THe extent to which he can be considered a threat on the global stage rests on the assumption that diplomacy and sabre rattling depend on one individual. THey dont.
Trump is not going to accidentally start a war any more than Bush made a decision to invade Afghanistan and Iraq on his own. There are many, many people at the table and it is their job to make sure that global peace isnt reliant on the President's mood.
Trump is simply a second hand car salesman.. These guys are all accommodating , will switch opinions, whichever way their audience is leaning and embellish at will, in order to push the deal over the line..