I've scanned the article. In some cases it is a bit unfair. I do think Americans are very generous, and some of the stats he quotes are unfair. The United States spends a huge amount on defense, but that money also is used around the world when disasters occur. Scandanavian countries are credited with giving more because they have a high tax rate and lots of social programs, but they give very little in the form of charitable giving. Because the church is state run, hardly anyone tithes.
With greater freedom comes greater risk and you see that in America. We are a land that has produced very good and very bad people. Because we allow greater freedom, we will always have more people that cannot use that freedom wisely.
But the article does give one pause.