I just made a reply to u/BooniesRedneck that would also work for your post. They were asking if there was a huge difference in population per county. Here is the reply I made to them:

Probably not each, but yes, they can be drastically different.

The perfect example is Virginia, and we saw the results of those huge differences in the recent redistricting election.

Remember the big deal that was made when Fairfax county reported their numbers late and swung the numbers from No to Yes?

Fairfax County has over a million people. This one county has more people in it than ~60 of the least populated counties in the state combined. Not 6. 60. 6-0.

That one county, which is overwhelmingly democrat, negated ~60 republican counties, many of which only had ~ 2,000 to 5,000 people.

Virginia only has around 95 counties. And Fairfax isn't the only example here.

Prince William county, democat, ~500,000

Loudon county, democrat, ~400,000

Arlington county, democrat, ~250,000

Those three counties have more people than the next 20 smallest counties (after the 60 I mentioned above) which are mostly Republican.

That's 4 democrat counties that effectively negates ~80 republican counties, because of the huge difference in population. Remember Virginia only has ~95 counties.

By physical size alone, those 4 counties don't take up anywhere near ~80+% of the state.

So the map showing lots of red doesn't mean that there are a lot of Republican voters in those areas. Because land doesn't vote. People do, and they're not evenly distributed across the state.