I was stopped and extensively questioned upon entering the U.S. from Canada via land border. I am an American citizen who was taking a roadtrip to Canada with my own car from California. Why did it happen?

The queue of cars at the port of entry was rather short and most of the other cars were Canadian.

The primary officer referred me for secondary inspection without giving me any reason. The secondary was empty so I walked straight to the CBP greeting them with warm "Hello". They needed to express their superiority by yelling at me that "we haven't called you yet!". Bossy indeed!

Then I was asked bunch of question about my trip to Canada. They took my car keys and went to search my car while I was waiting inside the room. It took them good 20-30 minutes. No idea what took them so long. (A conspiracy theory, could they plant a devide in my car? )

After they returned they stamped my passport and the exit card form and I was on my way out. I asked but they gave me no reason for the extensive search, only "We just wanted to enjoy your company".

Funny thing is there was nobody else but me at the time. Why did they pick me? Why did they choose to harass their own citizen?

Will this happen again when I cross the border? Am I flagged in a computer somewhere?

I was not expecting they'd lay out a red carpet for me but a nice words like "Hello and welcome home" would make my day better. This experience left a bitter taste.

Is this typical? Anyone with similar experience? Sorry I know this forum has to do mostly with flying, but I figured it might be somewhat relevant still.

It doesn't sound like harassment to me. It sounds like a routine customs search, and was likely random.

If it happens repeatedly, and you have a clean record with CBP, you could try to determine a reason and look at DHS TRIP. But being sent to secondary and a vehicle search happens at the US-CAN land border fairly regularly.

What was the harassment?

A routine secondary and vehicle inspection at the land border is exactly that, routine.

Let us know when you find the device they planted on you and what exactly you do that would interest them.

Well "harassment" is that they were quite rude and didntd give me any reason for stopping me. It might be random but still I don't understand why out of 100 cars out of which 90 are Canadian they pick US citizen for inspection...

Probably because you left your vehicle. They usually have giant signs that say "Stay in your vehicle".

I didn't leave the vehicle until I was at secondary.

They are always rude. That's how they train them to be - to make you more scared of them and fess up to anything you may have with you. A tactic more than anything. If you have GE/Nexus, the attitude generally is totally different.

At inspection to CBP you're not a citizen. You're a potential "threat" to violating the laws. If you don't submit & defer to them it can get hostile very quickly.

The inspection was most likely random and if they only inspected foreigner's cars it would make smuggling/sneaking things in easier. Being consistently inconsistent is DHS MO. If it happens again you can get suspicious but most likely it won't happen again.

If that's your consistent experience, there may be a reason for it. I've made many land crossings of the US/Canadian border and never encountered a rude agent. They're not perky and friendly, but my experience is they're not rude. Maybe it's because I always have the appropriate documents in hand and answer their questions without sass, and no, I don't have GE or Nexus.

It is normal to check sometimes in order to be sure but obviously it does not mean that they have to treat you this way, that's not normal ...