it's indeed a distinction without a real difference, but terrorism is specifically targeted at civilians to produce some political outcome.
It's wild to suggest that terrorism against the US should not be responded with by military action - it's only the degree and targets that should be under debate.
This is foolish nonsense. An organized foreign army directing improvised missiles against your cities is very definitely conducting 'military action' and is a valid target for a military response.
that's a surprising thing to hear. where do you draw the line between terrorism and war? I see a distinction without much of a difference.