Do isis only target major western cities?

No, they're trying to make a brand.

I think they've attacked places in China

They are going for the most media attention, The bigger the target the more attention they will get. Most terrorists probably couldn't even find Scotland

*etc., not ect.

Probably not. But here's the thing about ISIS. They don't actually have the capability to travel to places and carry out attacks. They make threats hoping that some disgruntled person who's already living somewhere will be inspired to carry out an attack- like the two brothers in Boston. So it's a little difficult to predict. But you have to put things in perspective. 4 attacks in Paris took out 126 people. That's a tragedy, of course. But it's also pretty pathetic for an organization that everyone is terrified of. A suicide bomber can really only take out the few people who happened to be near him. So you individual odds of being kills by a terrorist are still smaller than your odds of slipping in the shower and dying.