First of all, we have to remember that different books of the Bible were written either in different times, or with different agendas.

Specifically speaking about Jericho, Israel Finkelstein exposes his research on his book "The Bible Unearthed". According to him, the cities of Ai, Jericho, Hazor and Gibeon were destroyed/occupied in the span of many centuries, certainly not during a few years.

The wikipedia entry for "The Bible Unearthed" paints a nicely digested timeline of these cities.

With the conquest of Jerusalem by the Assyrians, it's a very different story: There's written extrabiblical evidence of the Siege of Jerusalem in Sennacherib's Annals, written around 690 BC. And there was another event, the siege of Lachish, in 701BC, that was described with extensive detail in a relief (currently held in the British Museum in London).

How can this discrepancy be explained? Well, taking into account that the Deuteronomical history was written during the 7th century BC (Finkelstein gives many details in his book to explain why he believes so), the conclusion's easy to spot: The writers of the books of the Exodus and Joshua were not eyewitnesses, and it's pretty probable that they did't know the history of the ruins they wrote about. And certainly there wasn't archaeology in those times.

Another archaeologist, William Dever, explains in his book, "What did the Biblical writers know and when did they know it?", that the Bible should be neither discarded as evidence, nor taken at face value, but studied as an archaeological artifact. So maybe we can't know about the times written about in certain books of the Bible, but we CAN know about the times when those books were written! (Example: If some books argue against a certain deity, it's reasonable to assume that at least there was some controversy surrounding such deity when those books were written; in a similar vein, if a book relates that a character fulfilled a prophecy, we can assume that such prophecy was known or believed by the people during that character's lifetime). I really recommend reading his book, it's enlightening. Speaking of Dever, he came to the conclusion that the Israelites never conquered Canaan, and neither did they migrate from Mesopotamia. Instead, they were natives of the land.