1. The claim that the Saudi government, that is to say the Saudi crown and the senior members of the al-Saud, as a matter of policy funded or supported al-Qaeda has been thoroughly disproved and can be rejected logically.
2. However, yes it is true that the Saudi's exported Islamism. This began in the 1950's and 1960's as a means to combat the rise of Arab Socialist/Arab Republicanism which was being used as a weapon by likes of Nasser to subvert and destroy the Saudi state. The cold war between Saudi Arabia and Egypt has only been matched in recent times by the one between Iran and the Kingdom. To fortify their rule in the face of assassination attempts, proxy wars, and attempted coups the Saudi's retrenched their religious credentials and created a network of allied Islamist parties abroad. However, this is not the same as funding al-Qaeda.
3. That Wahhabism originated in Saudi Arabia is not a guilty verdict that can be thrown at Saudi Arabia. It is an extremely orthodox brand of Islam to be sure, but it evolved in the 1700's in the circumstances of its time and arguably became much more extreme after the death of Ibn al-Wahhab. Moreover the modern incarnation of extreme Sunni Islamism in Saudi Arabia is tied to the Ikhwan and their position in the Kingdom and the circumstances of their dissolution and defeat at the Battle of Sabalah in the mid 1920's. The evolution of the deeply orthodox demographic in Saudi Arabia and the power of the Ulema and the clerical establishment is complex, but suffice to say they are extremely powerful and it is wrong to conclude that the al-Saud rules without checks or considerations from this sector.
4. This leads into the fourth point which is that for all its drawbacks the al-Saud have arguably been a modernizing and moderating factor in the Kingdom, especially King Abdullah. Though what the future holds remains murky.
5. It is widely acknowledged that Saudi Arabia made significant progress in its efforts to combat money laundering and illicit donations, going so far as to shut down most donations abroad altogether. That it is still a problem is more related to the fact that this is where many groups have domestic ties to and bedrocks of sympathy and that the money exists.
6. Saudi Arabia more often than not has been at the forefront of supporting US efforts in the region and abroad. They have backed and supported us in Afghanistan (twice), the Israeli-Palestinian conflict, Yemen (complicated but arguably yes), Lebanon numerous times, Syria (with independent but congruent interests), Egypt (during the Cold War), Nicaragua, Iran, the Soviet Union, oil prices and crude ouput (quite often with OPEC), etc.