Actually the impending British raid was known impending for about a month or so.
The then insurgent leaders had already dispersed their weapons cashes all over the area weeks before the raid. What was not know was the exact route(s) the British would take.
And that job of exact route warning was entrusted to not only Paul Revere, but to a variety of others too. And of all of them, only Prescott made it all the way through to Concord without being slowed. It was a giant advantage for Prescott because he was a resident of Concord, and could choose little known routes to evade British agents.
In terms of the British, they had a sound military plan, but because of advance warnings it was nothing but a busted play. There was no concentrated Arms cache to be found. And there was no bragging or taunting by Revere after he was captured, he deliberately inflated insurgent numbers, as nothing but a self serving bluff that worked. The Brits released him but gave him a tired horse, who could blame them, formal hostilities had not yet broken out.
Nor is Palin correct in her implication that Revere was trying to intimidate the British. Only later was the implications of the tactics obvious, that the Brits faced an insurgency war. With tactics little different than facing the Taliban today. The classic occupying power dilemma, a strong kick ass military that can occupy and control any given place, but far far too few troops to be strong everywhere. And every where the British were strong, our forefathers were smart enough not to contest.
But the key to the victory was British arrogance, when they lost the support of the ordinary American colonists, its was just a matter of time.