Bin Laden became angered at the United Stated when we continued our presence on Saudi soil after the Gulf War. He has rhetorically stated that the problem is our occupation of the land with 2 of the most holy sights in Islam.
In actuality, he has declared that the House of Saud should be replaced with an Islamic Theocracy. The presence of US troops on Saudi soil makes his mission much harder.
This isn't about westernism. It isn't about the Crusades. It's about power. Bin Laden wants it, and he sees our presence as a hurdle. The rhetoric he has used regarding the west and Israel is simply to make his cause more noble to his fellow muslims.