According to many unbelievers, there was a time in history when almost everyone believed the earth was flat, and the Bible reflects this view. Therefore, far from being the inspired word of God, the Bible is just the uneducated guesses of ancient man, and so it's just not worth listening to. Like most atheistic arguments, this one is based on ignorance of history and an incorrect exegesis (or more likely a very convenient eisegesis) of the Bible.
First, there is no evidence that the flat earth view was ever commonplace, whereas there is a world of evidence (pun intended) that it wasn't. While it's true that there were some who believed in a flat earth, such as Lactantius and Indicopleustes, their views were not typical. Rather, the round earth was the virtually unanimous belief of prominent Jews and Christians from the prophet Isaiah (Isaiah 40:22) to living Bible-believing scientists like Dr. Robert Carter and Dr. Jonathan Sarfati.
It's also worth noting that even today, as the Flat Earth Society is gaining ground, there are no prominent flat earth Christians. Quite the opposite, Daniel Shenton, president of the Flat Earth Society, is an ardent Evolutionist. To my knowledge, the only prominent "Christian" flat earthers also reject the Trinity, meaning they're not Christian at all, and are certainly not qualified to interpret the Bible.
Furthermore, it seems we can actually trace the origins of the Flat Earth myth. In 1828, a man named Washington Irving, who admitted he was "apt to indulge in the imagination", wrote a book called "The Life and Voyages of Christopher Columbus", in which he claimed that Columbus was told he would be unable to sail too far without falling off the edge of the earth. In reality, there is no evidence that Columbus ever faced such opposition.
But atheists can still attempt to salvage this failed argument by pointing to verses they think proves the Bible says the earth is flat. It is often claimed that there are actually more than 200 such verses. Now, obviously, I'm not going to waste time going through all 200. I'm simply going to comment on the fact that whoever wrote such a classic example of elephant hurling had too much time to waste, and waste it they did.
Then I'm going to lay the groundwork for explaining some of those verses. Specifically, I'm going to explain the concept of "homonyms". A homonym is a word which is spelled/pronounced in a similar or identical way to another word with a completely different meaning. For example, bear, bear and bare. A bear is an animal. To bear means to carry, present, or hold. To be bare is to be empty or uncovered. These three words are all identical in their pronunciation, and similar in their spelling, but they all have different meanings.
Biblically speaking, the same is true for the words "earth" and "world". In Genesis 1, verse 1 says God created the heavens and the earth, referring to the planet. In verse 10, however, God specifically calls the dry ground, distinct from the sea, "earth" (NIV users, please note that the NIV is distinct in its rendering of the Hebrew word "erets" as land rather than earth). We actually do the same with even small patches of dirt in which we plant seeds. We fill flower pots with "earth", this does not mean we are placing the entire planet in a tiny pot just so we can grow a daffodil.
Similarly, "world" can be used to describe the entire planet (e.g John 17:15), but it can also be used to describe the human race (e.g. John 3:16), the unbelieving portion of the human race (e.g. John 15:19), or a locality under a specific governing force (e.g. Luke 2:1).
Another homonym is the word "foundation". This can mean a thing upon which another thing, usually a building, is fixed, like the hard surface on which your house is built to prevent it from sinking into the ground, but it can also mean when an idea is formulated (e.g. John 17:24), such as the foundation of America as a nation.
One particular verse that can't be simply explained as a homonym is 2 Samuel 22:16, which says "Then the channels of the sea were seen, The foundations of the world were uncovered, At the rebuke of the Lord, At the blast of the breath of His nostrils." To the untrained eye, this seems to suggest that the earth, whatever shape it is, is fastened to something. But if we go all the way back to verse 1, which is always a wise strategy to employ, we see that this is actually part of a song that David was singing to God. It is not a literal description of what happened. It must be understood that, just like in English, Hebrew literature uses poetic language. The Bible actually has quite a lot of poetry inside it, with an entire book, containing 150 chapters, being named "Psalms". These Psalms, while designed to convey truth, do so in a poetic manner, with some of them even explicitly intended as song lyrics. One need never apply such a wooden interpretation to the Psalms.
Aside from poetic language, the Bible employs what is known as the "language of appearance", again, just like we do. We would all find it extremely infuriating if, instead of simply reducing things to a simplistic explanation, we had to trouble ourselves with scientific accuracy. Are the common terms "sunrise" and "sunset" indicative of the popularity of the geocentric view? Not so, we say them because it's easier than "the time when our particular region of the earth is facing in the direction necessary for us to receive light from the sun". What's especially ridiculous is that the geocentric model isn't even the same thing as the flat earth model. Ancient geocentrists still believed the earth was round. This is yet another way atheists inflate the number of flat Earth verses.
We see, then, that the argument from the flat earth myth falls flat itself. The Bible doesn't say the earth is flat, which is why the flat earth interpretation is so extremely rare, and always has been. Although there are some verses one could try to use, the context of those verses invariably shows that they are not trying to teach a flat earth.
But far more important than the shape of the earth is who rules it? The answer to that question is the same God who created it. Literally everything under Heaven belongs to God (Job 41:11), and unfortunately for us as sinners, that includes us. But as rebellious as we are against God, His mercies are almost unbelievable, as rather than condemn us for our sins, He sought to save us. He sent His Son, Jesus, to walk the earth as a perfect man. On the cross, He took the wrath of God, and in rising again, He bought us eternal life. Now, all it takes to receive that eternal life is the confession of His Lordship, and the belief that God raised Him from the dead. Rather than bickering about astronomy, maybe we should be talking about that.