You will be subjected to the same security as every other passenger at the airport, but all US-bound flights are now subject to additional checks at the gate, which can a very long time, especially when you consider that passengers must now be patted down and have their bags searched.
You will have no problem with the camera in your hand baggage. I always carry my Canon EOS 400D and three lenses in my hand baggage and have never had a problem. If the bag is searched, make the person searching it aware of the contents. Some of these people can be heavy-handed and have little or no respect for your belongings!
Incidentally, where in the USA are you supposed to be visiting? I am currently living and studying in Orlando, Florida, and I have been here for 14 months now. It is a lot of fun. The theme parks make for a good place to escape to when the studying gets tiresome and the weather is great right now, too! Unfortunately, my time here is almost at an end, so I will be back in the UK by the end of next week.
One thing to be aware of is just how long American immigration can take. After a long flight, you'll want to get to your hotel and relax, but you might be standing in line for a long time, so be prepared!