How do I fight my uncle in another state for my father's assets that was left to us?

You must obtain the help of a lawyer in the state where your father passed away.  I do not know what assets your father had when he died or who was "on the title" to those assets (like a deed to a house, bank account, etc.).  If your father was the only person on the title, then his children should inherit before his brother would inherit.  However, if his brother was on the title, he would now own the assets.

I hope this helps.  Please talk to a lawyer about it in more detail.