What factors were not present in Africa or the Americas to foster expansion into the Atlantic basin from those areas?

Because Europe is a big peninsula surrounded on 3 sides by oceans and having heavily indented harbors all along it's coasts. The earth is 71% ocean, so Europe has earths best launching pad for exploration / trade by ocean.

It's land connections with Asia, Mideast provided Europe with a top notch civilization and technology.

Europe was a very successful place for human population and concentration, so that it was getting overcrowded.