Complex sentence: This would mean that they would have to expend a lot of fuel to get there, and would not be able to come back to Africa and onward to find more habitable lands if the U.S. was like Europe, the ship would simply be trapped.
Split into simpler sentences: This would mean that they would have to expend a lot of fuel to get there, and would not be able to come back to Africa and onward to find more habitable lands. If the U.S. was like Europe, the ship would simply be trapped.