There are a variety of plausible reasons for this.
Israel is supported by many of the governments of the countries in which these protests are occurring. Protests might be more likely in places where people feel like they might actually exert a policy impact.
Israel is also extensively covered by the international press and, critically, English-language press.
Conceptually, I suspect most Westerners have internalized the idea of Israel as “one of us” and react to Israeli crimes as belonging to “our side,” with a concomitant sense of personal responsibility and sense that Israel might actually listen.