Gaza is not Viet Nam. Viet Nam is some 13,000 km away from America, Gaza is considerabley closer. Hamas need not be defeated, you're probably right, it would be very hard to do so. But they can be persuaded that certain actions will cause them a disproportionate amount of grief that they would be better off tweaking their philosophy a bit and recognizing certain realities. Then maybe we could all save some blood and treasure.
U.S., allies conduct 1 air strike in Syria and 11 in Iraq against ISIS militants (Reuters)
from the article: IDF chief: Gaza war against Hamas was an 'excellent' operation