There are not enough US troops to secure all these potential targets either (unless they are brought home from most of the countries they are in-- something the current administration is unwilling to do). So they will have to be foreign troops.
The reason this law change is needed is so the National Guard will not have to walk around with empty rifles, as they now have to do because of the posse comitatus law.
It is my understanding that the Guard had loaded weapons at most airports, when they were there.
And for that there needs to be a precedent. Thusly, NATO troops in Serbia/Kosovo breaking ground as the first multi-national force inserted into the affairs of a sovereign nation.
The plan marches on.