As a sibling commenter noted, Islamophobia is probably the common word used in US media for this concept. Islamism, by contrast, is typically used in the English-speaking world to refer specifically to the ideological movements that hold that Islam should be the basis of political systems (that is, establishing explicitly Islamic states; implementing Sharia as the basis of state legal systems; etc). So anti-Islamism, then, would carry a different meaning than Islamophobia or anti-Islamic or anti-Arab sentiment more generally.

"Islamophobia" is in fact a widely-used English word. (But it doesn't quite mean the same thing as "prejudice against Arabs", since "Muslims" and "Arabs" are different sets).