So what precisely do you find sinister about US P-3's assisting in the search? If we have we have P-3s in the region, it seems an natural and obvious thing to have offered their assistance. You're aware that the purpose of a P-3 is locating things in the water, right? and as such, would have relevant capabilities to offer? I'm at a loss for how you possibly interpret this as indicating a conspiracy.
If there's a hint of a conspiracy it'd be the mere fact of a search going on in The Malacca Straight. Not who's in fact searching - at least that's my take.
It's not a very logical place to look for a plane gone missing en route from Kuala Lumpur til Beijing - specially considering the last position of the plane as reported by FR24.