All Americans, unless I am mistaken.

Most, but not all, Kevin. A simple web search will turn up whole bunches more from Europe, Asia, Australia & etc.; I didn't have time or room to list them all. Google "Christian Terrorists" for example.

The ideology that might be more relevant might perhaps be American Exceptionalism.

Nothing to do with "American Exceptionalism" - these guys are all professed Christians and brag of/are proud of being such.