During the cold war, the US armed and supported radical islamist factions called mujihadeen because they were opposed to the communists. This didn't help, but ofc there were other factors. When the US began its wars in the middle east in earnest, they killed a lot of people including civilians. As a consequence, they were probably the most effective recruiters for radical islam (when a foreign government kills your friends or family, you'd feel positively incluned towards fundamentalist groups fighting them too). Throughout the iraq war and the related conflicts analysts warned that us intervention was fuelling islamic terror. I was under the impression that by now this was common knowledge.

For a big part, yes. Overthrowing democratic governments, funding radicals and bombing civillians tends to make people join the side that is seen as the enemies of the culprits of these crimes.