Pakistan, maybe, seeing as they have at times supported the Afghan Taliban and AQ.
I'm toying with a timeline in which this happens. Essentially, the Soviets (sort of) successfully conquer Afghanistan in the late 1980s, causing Pakistan to drift further toward Islamic fundamentalism, giving refuge to fleeing mujahadeen and continuig to support insurgencies in Kashmir and Afghanistan. This gets even worse throughout the 1990s, as the US effectively abandons Pakistan in favor of better relations with India, partly as a result of US detente with a surviving USSR. In 1999, an alternate Kargil crisis boils into war with India, culminating in a limited tactical nuclear exchange (under 10 warheads). The US and USSR mediate a peace treaty that heavily favors India in a number of ways and dismantles the fledgling Pakistani nuclear program. Smarting from a crushing defeat and national humiliation, a new hardline Islamist regime arises that sponsors and offers sanctuary to numerous Sunni terrorist groups, including al-Qaeda.
It's very vague so far. Still working on it.