KABUL, Afghanistan (AP) — Insurgents killed two U.S. troops in Afghanistan on the anniversary of the 9/11 attacks  on Thursday, making 2008 the deadliest year for American forces since U.S. troops invaded the country in 2001 for sheltering Osama bin Laden. The deaths brought the number of troops who have died in Afghanistan this year to 113, according to an Associated Press tally, surpassing last year’s record toll of 111. Afghanistan was the launching pad for al-Qaida’s terrorist attacks on Sept. 11, 2001.