Hi,
Your eagle sounds like a 1st year bald eagle. They typically have light tails with dark tailband and white extending from the armpit out. Ironically the first year bald eagle are much larger than the adults, because of the size of their 1st set of flight feathers. During second year molting, if you see one flying it will have an irregular bow shape at the back of the wings, this is because they have a mixture of 1st and 2nd year feathers.
If it was a second year, it would be a lot whiter underneath, and 3rd year has a distinct triangle on the bottom aft of the head underneath. They don't achieve the full white head and tell until they reach maturity in their 4th year.
In contrast the golden eagle has white patches on the outer area of the wings in their 1st year, and are generally darker in future years.