U.S.: NATO has intercepted Iranian arms

[mrdevious]

If this is all it takes to justify an invasion, then aren't there more than a few countries that would be justified in invading the United States?

Yep. The US has armed many militias that overthrew governments, often democratically elected governments, and then installed dictators. If the democratically elected government that was being overthrown were to invade the US on such premis's, I'd say they have full rights to do so. Of course the U.S. isn't about to dick around like that with nations that could actually retaliate on the scale of invasion.