Question

what might happen if Christopher Columbus had not discovered America and Vasco da Gama had not found a sea route to India

Answer 1

Columbus would have found another place and Vasco would have found another place

Answer 2

Hey there!!
You have asked a very interesting question...
Well for the first one, if Christopher Columbus hadn't discovered America, sooner or later someone else would've have found..
For the second one, if Vasco da Gama hadn't found a sea route to India, it would've created much problems among the Portuguese.. Because the main reason for discovering the sea route to India was flourish trade with it in terms of India's spices and silk. Since the Ottoman Empire had blocked the trade route to India, the European countries were forced to discover new sea routes...
But considering both of your questions, it can be said that even if both of them hadn't discovered their respective places, someone else would have have found them sooner or later.. But the major impact it played is that the more sooner they discovered their respective places, the more it began to help the society..
Hope it helps!!