Manifest means obvious to everyone and destiny implies a higher power makes things happen in a preordained way. It's fate. In the case of Manifest Destiny, it was originally about expanding this country across the continent to a supposed preordained size. The idea is that divinity ordained this country to be a certain size, and people needed to see that vision and then step out on it.
You would have to believe in an involved god to buy into Manifest Destiny because destiny, like fate, is about something bigger than us, about a force that will make things happen which we cannot (or at least should not) alter. Then you'd have to believe that god had a specific plan in mind for the world and the United States was/is to be his tool.
This concept of divine destiny for the United States is not in the Bible. In fact if you look at the Book of Revelations, when you come to the end times, there is no reference to any power coming from this region at all. Some, who believe in the prophetic nature of Revelations, think that is because the United States will have had a catastrophic event taking it out of the picture. If you instead think there is no reference because at the time it was written, there was no United States, then you likely also don't buy into manifest destiny anyway.
When you bring the phrase, Manifest Destiny, into today, there are those who use the concept to say it is the godly obligation of this country to spread liberty (never mind that we have lost a lot of our liberties supposedly to keep us safer) and democracy (never mind that we don't have a true democracy but a representative government) around the world. To a certain group, it is a godly command as though he had pointed a finger and demanded it.
There is a difference between knowing you have been blessed and wanting to share what you can with others and feeling you must do it as part of a divine plan. So here comes the question:
Was/Is Manifest Destiny an illusion or a fact? Is its concept helping us to do wise things as a nation today or hindering us?
The painting was from 1872 of an angel guiding the Mormons across the nation to their own Manifest Destiny.