I used to have long hair and got frequently picked out by security on my business trips to Washington DC. As soon as I got in line for the x-ray machine they would mark my ticket. Next please stand in this glass box while we search all your luggage, then get a thorough search over yourself.
I got so sick of it I rather drove the 9 hours from Canada to Washington DC. Not that that was much better. Since I was still travelling on a Dutch passport (was a permanent resident at the time) they took my passport at the Buffalo border crossing. I had to wait in a concrete waiting room for an hour until my name was called for questioning, pictures and fingerprint scans. Then buy a 6 dollar visa waiver. Welcome to the USA. At least on the way back into Canada I could drive straight through.
Same thing happened on our honeymoon when we crossed into the states from Vancouver to Seattle. Car got a thorough search while we had to wait and not cross some line in an office building.
First time I drove over the border I didn't know about the 6 dollar fee. I had flown to Montreal and was driving down to a business meeting in Hanover Vermont. (Beautiful drive in autumn) I had filled out the visa waiver at the airport already, but they ignored that. (Exact same form) They only accept cash, so I had to walk back across the border to a convenience store and exchange money. Welcome indeed. They should just post a big F... OFF sign at the border.
My most 'suspect' trip caused me no trouble at all in comparison. Once I got on the wrong plane (yes it can happen lol) and ended up in San Jose, Costa Rica instead of San Jose, California. I had no problem arriving there without a visa, got right back on the plane home without a problem, no problems arriving back in Toronto after a round trip in a day, just some good laughs.