I looked into this several years ago as part of my geneaological studies in my home state of Virginia. At the time, I had no idea of the political ramifications of what I was finding. One bit of "evidence" I read about was that someone claimed a Native American tribe in VA wore fez hats much like those worn today in Morocco. However, there IS evidence that Arabs could have preceeded Columbus. Chris found the rotted hull of a ship on one of the islands (I forget which) that looked like the design of an Arab vessel (I forget its name). One source I read said that Samuel Morison, eminent American and Columbus historian, had mentioned it in his writing. And so he did. He rather dismissed it, but he did note that Columbus mentioned it in his writing.
So, yes, Arabs may have preceded Columbus. I personally don't think its all that significant because I think there is evidence here that lots of people preceded Columbus. But it was Columbus who was fortunate enough to get here after the invention of the printing press and who was insightful enough to grasp the enormity of what he found to do something about it--begin settlements.
While the Algouquin Arabs sound like a Blazing Saddles outtake there is nothing inherently absurd in the notion that some Arabs made it to the western Hemisphere before 1492. Little as I like the Arabs one has to acknowledge that thier progress as mariners was astounding. From being camel jockeies they already were familiar with using the stars to navigate across the 'dry ocean' of the Arabian desert.When after conquering Syria and Egypt they were introduced to sailing vessels and ocean voyaging they enthusiastically took to the sea and became the boldest sea raiders since the Vikings. People who raided (often) as far north as Iceland for slaves and had a regular commerce across the Indian Ocean could easily have reached the Americas at some time. However, the long overocean voyage, rough seas and difficulty of hauling any unfortunate Indians back as slaves would all militate against this being any more than an exploratory mission that determined the western lands weren't good pickings for the faithful.