Visit the Marine Corp museum in Quantico Va. You could walk around that place for hours and not know that the USA even had Navy.
The very word “Marine” defeats your argument. The word seems to have something to do with the sea. likewise, the Merchant Marines.
The origin of the Marines traces back to the Royal Navy and the Royal Marines. Check out the Horatio Hornblower series on youtube. they depict the Marines, dressed out in red, as sea soldiers, always operating in conjunction with the Royal Navy.
Whether US sailors and marines like it or not, the US Navy and Marine Corp tradition derives from the British Navy and Marines. Where does the color of US Navy (blue) and Marines (red) uniforms come from, but the Brits? Along with a great many other traditions.