It is dangerous for a country to appear weak. Ukraine is going through hell because Putin thought invading it would be a walkover. 9/11 made America look weak a

It is dangerous for a country to appear weak. Ukraine is going through hell because Putin thought invading it would be a walkover. 9/11 made America look weak and incompetent (the U.S. did not control the airspace over the Pentagon?), so the country had to respond more strongly than to some other calamity that caused a few thousand deaths. Of course, this does not mean that everything precipitated by 9/11, such as the war in Iraq, was a good idea.