The first sentence of that article says "While almost all U.S. businesses (97 percent) say they offer some form of severance to workers, only 55 percent had formal, written severance policies last year, a decline from 2011, when 65 percent had formal severance policies."

That seems very not universal. Just because a company says something doesn't mean it follows through, and if it's not formalized it's worthless. A longer notice period both ways seems preferable. Besides, in the EU it is common to take paid leave for a large chunk of that notice period so in addition to having time to tie off loose ends and leave on good terms, you often don't have to work out that whole chunk of time if you don't want to.