goldfinger0303: 'Terrorism' is not well defined. For instance, the traditional definition of terrorism limits it to state actors (today called 'state terrorism'). Through this lens, the U. S. military is by far the largest actor which commits acts of terrorism on the world stage. If you accept Henry David Thoreau's arguments in "On Civil Disobedience" (paying taxes is active support for unjust actions of your state), then the largest constituency of terrorists are the U. S. taxpayers.
Even using the new definition of terrorism (which limits the term to non-state actors and states in rebellion), your claim that >50% of 'terrorists' are Arabs is flimsy. Firstly, estimates of the Islamic State's strength are not reliable for a variety of reasons (not least because an organization that large requires a civil service). But even taking your 200,000 figure at face value, let's compare it to other groups: Naxalites count around 20,000, CPP around 5,000, PKK around 5,000, Boko Haram around 9,000, ELN around 2,000, FARC around 9,000, Shining Path around 500, Pakistani Taliban (TTP) around 35,000, Caucasus Emirate perhaps 1,000, Al-Shabaab around 5,000, Balochistan Liberation Army at least 500, Movement of Democratic Forces of Casamance around 2,000, Donbass pro-Russian separatists around 20,000, FDLR (Rwandan Hutu rebels in the DRC) around 2,000, MNLF perhaps 10,000, EPP (Paraguayan rebels) around 150 . . . Okay, I give up. This is taking too long. There are many more groups that fit the bill, but it takes too long to find semi-reliable estimates. And this is without counting the dozens of insurgent groups (with many thousands of members) in Northeast India, Myanmar and South Thailand, of which little information is available.