+1(514) 937-9445 or Toll-free (Canada & US) +1 (888) 947-9445
It's not fraud -- just keep crossing the border every 6 months, and if they take away your green card, they take it away. I know people who have kept one up for a long time, look for opportunities to spend time in the States for longer periods. This almost happened to me, I'm glad it didn't.
 
Have not done so far but I am afraid. Had a hard experience even on H1B.
They can ask even when coming to US from any other country.
The Canadian Permanent residence visa is stamped in the passport. very tricky situation.
Planning to give up Canadian PR. Can any one guide how I can do this?
Thanks.
 
I have a friend who is doing the six months thing and last time going back to the US, she was pulled in secondary inspection for two hours. She expects the same thing from now in because the CBP documents everything these days.

Also since the OP mentioned living at a border city, beware the first dead giveaway to the US CBP is your Canadian plate, and the reverse is true if you have a US plated car coming back. Put it simply, they will ask how you can claim PR in one country while living in the other evidenced by where you registered your car. You register your car where you live. So be careful.