The Founders gave the Congress and the Executive branch broad powers for dealing with the real world. Despite their non-intervention beliefs, they took the fight to the Islamofascists of their day. They understood quite well that Washington could not have won the revolution without our collaboration with France. You read their words but you failed to understand them. It happens.
Can you show me in the Constitution where the Federal government has sufficient authority for one but not the other?
You object to our foreign policy. It is clear (to me) that the Federal government has all the authority it needs to conduct the foreign policy it sees as correct.