ACCORDING TO the Muslim, Muhammad Hisham Kabbani, who testified before the U.S. State Department, 80 percent of mosques in America preach "extremist ideology."
Coming from an entirely different source, the Mapping Sharia Project sent trained people into mosques in the U.S. to find out how many of them are calling for jihad against America. They discovered that the majority of the mosques they've investigated so far do, in fact, promote jihad against America, in the Friday "sermons" (known as "khutbah") and in the literature available at the mosques.
In a speech by Mark Steyn, he said (when answering a question) Canadian Mounties did a survey of Canadian imams. It found 85 percent of the imams in Canadian mosques were "hardcore radical jihadists."
Saudi Arabia's oil wealth enables it to control around 90% of the world's Islamic institutions (source), and the Saudis promote hardcore, fundamentalist Islam. They pay for these mosques because it gives them control over what is taught and promoted at the mosques. Read more about this.