I am planning to buy a Pontiac bonneville 2004 my question is about it parts the dealer told me it is parts is the same as GM and can be found easily in US. Is that right?
Pontiac is a GM brand of vehicle, so yes, GM parts will fit your car. Pontiac parts are not hard to find in the States ... pretty much any parts shop will have them or can get them. Not going to talk about prices, as that would make this off-topic.
In addition to being easily found locally, there is a huge online marketplace for you to buy parts from too. I know I can't say who or where (or at least I think I can't). That said, depending on what it is, finding parts online and having them shipped to you can often be cheaper than going to the dealer.