Greetings Cosmic Americans!
A troubling, but common way to look at Union victory in the Civil War is to reflect from the vantage point of 1865. From there you can easily trace Union advantages and illustrate how victory seemed inevitable from the start. One of these great advantages: the United States had a navy ready to attack when the war broke out.
Or did they? In the film Gone With the Wind, Rhett Butler forecasts doom early on stating, "The Yankees are better equipped than we...they have a navy to bottle up our harbors and starve us to death." Well...eventually, the navy played an important part in Winfield Scott's "Anaconda Plan." It blockaded seacoast harbors and menaced cities and installations on Confederate rivers. But in the spring of 1861, the Unites States Navy was only a shadow of what it would become. Their upwards of 70 ships were either not serviceable or scattered around the world. In fact, when shots were finally fired in April 1861, only a handful of U.S. ships could be brought to bear on Confederate forces. What's more? in 1861, the U.S. Navy was a deep water fleet - and could not navigate along the rivers that were vital to the Confederacy.
So yes, having a navy was an advantage from the start. The Confederacy had none, and had to build one from scratch. But simply having a few ships ready for duty could hardly be called a decisive advantage. And so without the benefit of reflection, one might think of the U.S. Navy as enlisting only a slight advantage. Northern manufacturing capacity was the real clincher - the ability to build rapidly and commission a vast navy ultimately meant that the United States could put to sea a formidable fighting force in relatively short order...far more destructive than anything the Confederates could muster.