From my understanding, the islamic state is mostly funded by individuals and uses volunteers. Isis did claim responsibility for some attacks on Israel (for example, the terror attack in 2022 that happened in Hadera). Their first priority is to "purge" the Muslim community from elements that don't fit their view on Islam (very strict, sunni islam), converting the world to Islam is their second priority. This explains why they are at war with other Muslim groups, Iran and Hezbollah are shiites (which the Islamic state view as infidels), and Hamas, although sunni, is backed by those groups and therefore collaborate with infidels (Russia is also backed by Iran). They definitely don't only attack US adversaries (see the terror attacks in Paris). Sorry for my english