I’ve watched a few times. It’s pretty funny.
Cop:
Where ya headed?
Brian: we’re uh going to get some Thai food
Dad: well we’re coming from wsu
Brian: yeh there was a swat team there (trying to keep the subject off Idaho murders i think)
Cop: what’s wsu
Dad: Washington state university
Mentions bryan getting phd there
Bryan and Dad: Talk more about the swat team and shooting incident. dad says he’s horrified by it
Dad: we’re going to Pennsylvania in the pocono mountains
Bryan looks at dad like WTH, dad?!
So basically i think this video is being used as evidence to show how Brian just says we’re going to get Thai food, ratger than we’re going home for Christmas to PA when asked where are you headed. I believe twice he’s asked and that’s his answer. He doesn’t want the cop to know where he’s going. He also doesn’t seem to want the cop to know where he’s coming from either.
Obviously, if you’re going on a cross country drive and someone asks you where ya’ headed, you give them your final destination, not where you going for lunch. You especially would tell the cop where you are headed and where you’re coming from to garner sympathy like “Look we have a long drive ahead of us and have been driving a long time. Sorry for the tailgating. Please cut us some slack. We will do better from here on out.” That’s exactly what the dad did. He wanted the cop understand that their “where ya headed” “where ya coming from” was DAYS of driving. Not just a trip for lunch.
Well, neither of the three is great at pragmatic, social, speech. Cop is trying to be easygoing, but I would often hear, "OK, I am heading to the house", or, "I am heading for lunch". Only "I am heading home" requires no preposition, so technically speaking, "heading for Thai food" is as good as "heading to Pocono mountains". Bryan is very concrete, but his dad is not much better, answering "we are driving from WSU" (equal to "head off").
Of course, the cop, standing in the middle of the road leading through Midwest, in interested in non-Indiana license plates, so technically, from or to, it is through Indiana that is important for him. He doesn't care about prepositions. Bryan's answer "for Thai food" could be calming ("we mean no harm in your state, just to spend some dollars on food here"), only I don't think BK is that deep.
We, foreigners, struggle with pragmatics. A teacher's report about my kid, "a pleasure to have in classroom", was a puzzle (is he so great, or there is nothing else to say about him?). And there is a whole list of "what Americans really mean" ("This is a brilliant idea, we surely should get back to it", means, no). Pragmatics are hard for people who grew up in a different culture. BK, being an American, should be able to navigate it easily. His dad, too. They can't.