Miért mennek olyan nyugodtan, szabályt betartva?

In the US, why do most people pass you when you're driving the speed limit? Isn't that illegal to be driving faster than the speed limit?

The speed limit is really just a suggestion.

No haha, it is the speed limit and speeding is illegal. The US has roads that are wide and banked and capable of high speeds. Unfortunately, in the 70s, the speed limit was reduced around the country to save gas. Even though the roadway speeds are a state issue, the federal government tied highway funding to the reduced speed. So states fell in line but really did not enforce the limits. For instance, NJ parkway speed limit was 55 yet no cop would pull you over for anything less than 65. EVERYONE knew this. NJ even got into trouble where the feds put up a monitoring system to see how fast people were traveling on the parkway and NJ answered by parking an empty state trooper vehicle right before it.

Anyway, now the speeds have come back up. However, many motorists got into the habit of speeding from when the speed limits were lower. If you are going 65 on the GSP, you should be in the right lane. Traveling at the speed limit in the left lane is dangerous to all who use the road. Left lane typically is around 80 mph without fear of a ticket.

So although cops will give you a little break on the speed limit, (a couple MPH) on the throughway/turnpike/parkway the break is significantly more (typ 15 MPH).

Still does not mean you won't get pulled over so it certainly is at your own risk. Good luck!