Why is obesity running rampant in the United States?

Is like eveyone sitting on PC's these days eating Pizza and McDonalds?

Everyone is busy and eating at fast food restaurants and not having time to excercise. Otherwise, they are just lazy people who don't want to exercise.

I think you are right and not enough exercise
To answer your first question, Its because its easy, To answer the second, I'm not.
I live right next to a Taco Bell.
Because it's one of those things you're not supposed to talk about, even though it's bad for you. Smokers have become demonized, for example, you can criticise them all you want, but you're supposed to pretend that fat people aren't fat and perfectly healthy...

Of course, what restaurant is going to ban tubbies? lol That'd be like christian youth groups banning virgins...
Some people are big because of genetics. Some people don't eat like they should. Nearly everyone is in a big hurry and they eat on the run. Moms work away from home and are not house moms like they were in 'leave it to beaver' days. So, fast meals from a box are today's convenience. As a big girl it is hard to lose weight. I catch myself eating too much because I eat in a hurry. It is a habit that has developed over time... I used to work in the medical field and we ate in a hurry and got back to our duties. Then I traveled with my husband, and we were always in a hurry when we ate. Now, I work in a field that 'networking' is important. So, I often eat with a client or someone that is in the business 'network'. I really need to watch my weight and my eating habits because my parents are both diabetics.
All of the above + sodas. When I lived in Wisconsin for 9 months, I couldn't believe the amount of soda people would drink during one day! I mean, people tend to do it in France, now, but it's definitely not the norm (although we are slowly getting there, unfortunately).