I am immigrant in Canada. I live in Montreal, I don't have Canadian Passport. I have Iranian Passport and with Iranian passport I must get a visa, and it is possible that officer reject me. I want know how can I go to USA with my PR?
While @Tom 's answer is perfect, let me add some personal experience (it's a bit long for a comment): I am a Hungarian citizen, I have a 10 year B1/B2 USA Visa since 2007, Hungary is visa exempt since 2008. I am also a Canadian resident since 2008. In 2009 the Canadian startup I was working for got acquired by a company in Denver and I became a senior software architect (still employed in Canada) and so I was going back and forth between Denver and Vancouver a lot. To add insult to injury I was also attending various tech events. This has gotten to the point where sometimes I crossed the USA-Canada border twice a week (OK, that only happened once, but once every two weeks was quite normal for months). In the spring of 2011, when trying to cross the border at the Vancouver airport, I got secondary questioning. I was allowed through at the end. The US border guards typically don't care a lot about my PR card, alas, when I present it, they don't want it. Since then I've gotten my NEXUS card, this wonderful skipper-of-queues so now it's easy. But I tended to use the land crossing instead of the preclearance at YVR before I've gotten my NEXUS and it was a lot easier (of course, taking a bus to SEA is a hell lot slower than a cab to YVR). Whether this is the same around Montreal I do not know alas but at the Blaine border everyone gets out of the bus and walks through the border and so there's a slight (quite probably very slight but it exists) pressure on the border guys to move people faster not to hold up a busload of people.