How long can the European discovery of the America's be delayed?

[Vulgarian]

As the thread title says. Staring probably after about 1000 AD, what's a realistically timeframe European discovery can be delayed?

 

[Salvador79]

With a Pod of 1000 CE, a lot is possible. Mongol devastations, followed by a worse Black Death... could be centuries.

Even with sabotaging Portuguese naval explorationism in the 1420s/1430s, you could still delay the discovery for a century.