You do not recall correctly. The single most pressing reason was taxation. The Stamp Act had nothing to do with postal service. If you contend that this is the case, then I encourage you to find this complaint in the Declaration of Independence, where the list of grievances is long.
Second, no one is being forced to show papers at random. He was asked at the gate of Southwest Airlines' very expensive plane. When he refused to show them, he was free to leave the airport.
Third, if he doesn't like it, he can buy or hire his own plane. There is no constitutional right to cheap travel.
The Stamp Act was the last straw.
It was the search and seizure used to keep the populace in line that weakened the camel's back to the point where it could be so easily broken.
The King's men were looking for smugglers, they claimed, but they were denying the colonists the rights accorded to all Englishmen.
Privacy is so basic a right that it wasn't even thought to be placed in the bill of rights. It was such a given to the Founders that only the details of protecting it were considered worthy of discussion.
Amazing how far we have fallen.
Enjoy your chains.
Actually, you don't recall right either.
The war started when the British marched on Concord and Lexington to confiscate the pesky guns that government tends to hate when in the hands of it's subjects, er, I mean citizens.