Much is made of Japanese gift-giving and how it occurs at the drop of a hat. I think that the ritualized and formal manner in which gifts are given tends to make it seem more frequent and obvious compared to western cultures than it actually is. If you examined the frequency of "gifts" in both cultures, I'm betting they'd actually come out pretty even.
When I say "ritualized and formal manner", I mean that nothing seems to be handed over casually in Japan. If you receive even a small item like a chocolate bar or a cupcake, it's usually wrapped in paper or at the very least given in a bag. In the States, we might give someone a souvenir or box of candy but we just say something like, "I picked up this (whatever) for you when I was in (wherever)." Such gifts don't feel like they're part of a gift-giving occasion because they aren't wrapped or hidden in any fashion.
The formal nature of gift-giving was brought home several days ago when my husband went to Krispy Kreme for some birthday-related donuts and decided to pick up a half dozen to give to the landlord and his family. Back home, this sort of "gift" is often casually handed over and the other party is thanked and that's it. In Japan, such acts often elicit either a return gift or a formal thank you note. This is rather a nice thing except that you can find yourself sometimes hesitating to give a gift out of fear of placing the other person in a position of feeling obliged to reciprocate. This isn't something we tend to worry about so much back home (except at Christmas).
The other thing which tends to make gift-giving in Japan appear more remarkable is that gifts are often given in the opposite situation as they are back home and they are offered more consistently because of social obligation. For instance, if a new person moves into one of the six units in our building, that person often (but not always) goes door-to-door to the other 5 tenants and gives a small gift like a tea towel or small food item (e.g., bean cakes, soba). In the U.S., a new neighbor is sometimes greeted by the the people in his new neighborhood with gifts. The concept of the "Welcome Wagon" is based on the idea that the new party is made to feel a part of the community through experiencing the warmth of neighboring people and businesses through gifts. In Japan, the responsibility is on the newcomer. In the U.S., the responsibility is on the existing social network.
With Christmas on the horizon, thoughts of western gift-giving habits aren't far from my mind. At this time of year, there's an explosion of consumerism, obligation and generosity back home (a time which starts earlier and earlier). Japan has no equivalent of the sort of excess the U.S. has in this regard, at least not on a personal level. The closest they come is winter and summer gift-giving but that isn't quite the same as it's largely confined to business giving and usually isn't personalized as it mainly involves giving gift packs of food, soap, or other utilitarian items.
The other big personal gift-giving situation back home, birthdays, tends not to be an occasion for giving gifts here either. When I ask my students whether or not they got many birthday gifts, most of them say they got one or none but just went out to a bar or restaurant with their friends. I sometimes feel a little bad for them when they say they don't get anything but then I realize they don't expect anything anyway so it's not a big deal to them.
Generally speaking, I think people in the U.S. give gifts in similar quantity but they tend to give them so casually that they're not seen as gifts and those gifts which are given as formal, wrapped presents tend to be tightly attached to two specific occasions whereas in Japan gifts are almost always formal and not necessarily closely attached to occasions.