What is the value of a 1776 US 2 Dollar bill?

I assume you're looking at the back of the bill where there's a picture of the signing of the Declaration of Independence. Please turn the bill over and look at the printing date on the front of the bill rather than the date of the picture on the back. You'll find that your bill is at least 2 centuries newer.

The back has an interpretation of Trumbull's famous painting of the signing which of course was in 1776, so the date is simply part of the caption.

If it's circulated, it's worth face value only. $2 bills are still being made so feel free to spend it.

Uncirculated, it would retail for about $3. A dealer would pay less.