Here's a rather stunning chart from the US National Climate Assessment 2018, Chapter 25.
It shows that since 1984, climate change has doubled the total wildfire acreage in the US west.
Note: the acreage is zero in 1984 because that's when they started counting. Results come from an ensemble of climate models.
This additional acreage comes to about 12 million acres, or 19,000 square miles. That's a little more than the area of Vermont and New Hampshire combined.