In response to the thread title, there is this excerpt from the article "Is Jihad Fard Kifaya or Fard Ayn?" posted on islamicemerate.com written by Ibn Nuhaas. I'd post a link, however, I'm unable to at the present time due to not having enough posts.
"This is all regarding the Jihad, which is Kifayah - a collective duty - (starting war with the non-believers on their territory). But if the enemy enters the Muslim land, or even approaches it and masses on its borders, even if they do not actually enter it, and their armies are double the size of that of the Muslims or less, then Jihad becomes mandatory on each and every individual. Then, the slave leaves without the permission of the master, the woman without the permission of her husband (if she has the strength to fight according to the stronger opinion), the son without the permission of the parents, and the one indebt without the permission of the lender. All of the above stated is the opinion of Imam Malik, Ahmad, and Abu Hanifah (in addition to the madhab of the author which is Shafii)."
The first sentence in the above quote makes it fairly clear as to why they feel they can attack any country made up of "unbelievers". The rest explains rather well the reason they're fighting "unbelievers" in their own lands. They feel they not only have the right, but that they're commanded/obligated to.
Please don't get the idea that I find their justifications/reasons/ideals acceptable, because I don't. I have nothing good to say about a religion that treats people (believers as well as unbelievers) the way Islam does.
I think the most relevant part of this quote is "But if the enemy enters the Muslim land,"
Flopper, I believe you missed the parenthetical statement in the first sentence of the article I quoted. "This is all regarding the Jihad, which is Kifayah - a collective duty -
*(starting war with the non-believers on their territory)*" Any country will react to being invaded and feel justified in reacting to such an invasion. Islam is not a country, it is a religion. That parenthetical statement is indicative of the goals of Islam. One of the difficulties with Islam is that Muslims feel that wherever they are is their country, which means that no matter where they are, they're being invaded. And before people jump on me, yes I'm aware that there are countries where Islam is the rule of the land. This does not in any way diminish the fact that Islam is a religion, practiced in many countries throughout the world and not just an area defined on a map.
One thing that I've seen consistently stated by Muslims of all levels of enthusiasm is that non-believers are inferior to Muslims and deserve whatever they get in the way of disrespect from Muslims. As far as I can tell, this is done for one of two reasons - turn the unbeliever into a believer or force them out. The consistent insistence on Sharia Law being adopted is an excellent example of that, and most of the West is too afraid of appearing to be insular and inflexible to stand up and say "No, that is not how things will be done in this country", firmly and politely. Americans in particular have cowered behind PC terms in order to not offend other peoples all the while not understanding that being PC is not the same as being polite or considerate nor realizing that some peoples will be offended no matter how PC, polite or considerate you are or try to be.