One was a revolution against a tyrannical king from across the ocean that killed 25000. The other was a war against fellow Americans from the south that refused to fall easily under the thumb of the DC empire politicians and lawyers that killed 650,000. Hopefully you now see a difference.
How tyrannical the British king was, in any historical sense, is at minimum debatable. George III was quite possibly the most decent human being to ever sit that throne, admittedly not a high standard to beat.
Our second civil war was against Americans who rebelled against a constitutional system they had themselves helped to set up, but in which they refused to accept the perfectly legitimate results of a free election, launching a horrific war in response.