I assume that what you are asking is, "Are American kids today overscheduled?" If you asked the same about Korean kids, I would say yes, almost definitely. But today, no, kids have a lot different issues to worry about than whether or not they are busy all the time.
The only real requirement is that kids go to school, after that, the activities they enroll themselves in are optional. I do agree with one of the above comments, that kids rarely even have time to eat, and thus they eat junk - but this isn't the fault of society or their schedule, it is the fault of their parents. There is a such thing as healthy snacks, and even healthy quick dinners. In fact, there are a lot of them.
When I was a kid, I had maybe one extracurricular activity, but I did other stuff at home. I also ate good and was expected (but not forced) to do my own share of chores around the house. I wouldn't have considered myself incredibly busy compared to my friends, but I was happy with this. But one of my friends had about 20 billion activities always going at once, and she was just as happy and healthy as I was.
So perhaps what you should ask if you have a child of your own is, "Is my child happy and healthy?" Many kids need a lot more to do than adults, they have more energy and learning capacity, after all. So just make sure to sit down for a real dinner when they do come home!