I did find the line about the Klingons a bit odd, even forgetting Enterprise... Only two worlds? Just seems like a minor threat at best. Unless we're talking about Federation member worlds. Which would mean the Klingons were actively invading Federation territory.
Picard referred to the "disastrous First Contact" with the Klingons, which led to decades of war.
We saw Archer go against Vulcan wishes to return Klaang to his homeworld in "Broken Bow" (ENT) and, later, the episode "Judgment" where Archer is put on trial and sent to Rura Penthe. Fans complained at the time that it wasn't nearly "disastrous" enough, but all those niggly things - and many offscreen events in the interim - could add up to disaster when viewed from the 24th century.
Lots of wiggle room for all manner of sabre rattling.