Would Christopher Columbus, in a hypothetical scenario where the north/South American continents did not exist, survived a journey to India? That is, would he and his ship crew been able to achieve a journey this long? Or were they actually saved by the landmass and islands of the Americas from a voyage that would’ve surely ended in death had they actually reached their intended destination? How foolish was their initial ambition exactly?
The short answer: No.
He was equipped for a voyage from the Canaries to the Caribbean, and not for the much longer voyage to Asia. It took him 35 days to sail from the Canaries to America (i.e., the Bahamas). The first sailing from Mexico to the Philippines, approximately the shortest continuation that would have taken Columbus to Asia, if the Americas were not there, too rather longer than that. The expedition, a large one of six galleons, left Mexico on 1st November, 1542, and their next landing was on 26th December 1542, in the Marshall Islands. Given that Columbus had supplies for a voyage of about 4 weeks one-way, so 8 weeks there and back (and would have soon turned back, if he hadn't spotted land), a journey of over 80 days one-way was too long.
Columbus was helped in his voyage by not expecting any land for 4 weeks, so he sailed day and night, which is dangerous in unknown waters. After reaching where he expected Asia to be, he would have proceeded more slowly and carefully, expecting to find Asia at any time. Thus, he would have not have sailed that much further before turning back.
While Columbus is sometimes presented as somewhat of a lucky idiot, for basing his voyage on a very short estimate of the distance from Europe to Asia via a sea route to the west, he did know that there was land closer than Asia. In particular, he seems to have visited Iceland in the 1470s, and there had been earlier expeditions to cross the northern Atlantic. The Norse colonies on Greenland had only been abandoned (or died out) earlier in that same century, and were still remembered. The 1473 expedition by Pining and Pothorst (on behalf of both Denmark and Portugal) had explored Greenland, and possibly also Newfoundland. A second attempt, in about 1476, again by Pining (and with pilot Jon Skolp), is thought to have reached the North American mainland.
Given that land, and Columbus's probable knowledge of it, he might have assumed that north North America was the far north-east of Asia, and that therefore the "useful" part of Asia should be roughly where the Caribbean is. Thus, while Columbus's first voyage would failed if the Americas weren't there, it is quite possible, even probable, that he wouldn't have sailed if the Americas weren't there.
Further reading on what Columbus might have known, and where he might have known it from:
Cortada, J. (1976), "Myths, Facts, and Debates: Christopher Columbus and the New World before 1492", Renaissance and Reformation/Renaissance Et Réforme 12(2), 89-95. http://www.jstor.org/stable/43464992
Hughes, T. (2004), ""The German Discovery of America": A Review of the Controversy over Pining's 1473 Voyage of Exploration", German Studies Review 27(3), 503-526. https://doi.org/10.2307/4140980 https://www.jstor.org/stable/4140980
There is more about Danish-Portuguese cooperation of the time, and Pining, Pothorst, and Skolp, in: Janus Møller Jensen, Denmark and the Crusades, 1400-1650, Brill, 2007.
Great answers! Thx for taking the time guys 🙏