As for Britain's war against the IRA, that was a local conflict, not a World War. The IRA did not fight all over the world. The IRA was specific to Ireland only, it wasn't an international organization like Al Qaeda or ISIS. Arabs identify by religion, Europeans identify by nation, that is the rule I believe. There is very little difference between an Arab living in Egypt, an Arab living in Syria, or an Arab living in Jordan, they speak the same language, and they move across borders hardly caring what their nation is called, that is why Al Qaeda was able to recruit so many people. the IRA by contrast has only been able to recruit Irish, there are very few French or Germans who are IRA members if any at all. The French don't really care about Irish independence, it doesn't concern them.
Northern Ireland was a religious sectarian conflict; the IRA identified with the Catholic minority, the loyalists with the Protestant majority. The IRA recruited mainly Irish, had links to world-wide terrorist groups, was funded, in part, by American-Irish and had training camps in Libya.
The Middle East is a religious sectarian conflict, Al-Qaeda and IS identify with the Sunni fundamental orthodox majority (albeit a radical group), whilst the current govt. in Iraq are fundamental orthodox Shia minority, as is Iran.
The Baathist party in Iraq was an inclusive progressive moderate government, as is the government of Assad's Syria (the uprising against Assad was started by an Al-Qaeda splinter group).
The governments of all of the other Middle Eastern states are fundamental orthodox Sunni (although Saudi Arabia and Jordan are a bit more progressive). To put it in perspective, the Taliban were also fundamental orthodox Sunni.
The USA has got itself firmly mired in the middle of a sectarian feud that has gone on since the death of Mohammad, between the Sunni majority and the Shia minority.
The reason that IS has been so successful at recruiting fighters from other parts of the world is that they are also Sunni's and can plainly see that their enemies, the Shia, have allied themselves with the USA.
The Kurds, like the Sufi's, see themselves as a separate group than either the Sunni or Shia. Saladin, who successfully fought against the crusading armies in the 12th century, was himself Kurdish.