Why are most inland states republican and most outer states democratic?

Answer 1

That is not exactly true. Most highly urbanized states typically vote, in the majority, Democrat. But it is the urban populations more than the rural populations that do.

States where urban populations are not in the majority typically swing Republican. Some states like, Texas and Florida have high urban populations, but Texas typically goes republican and Florida often goes either way. California with a highly urbanized coastal population also has a highly rural population in the southern valleys that vote democrat while a somewhat urbanized north valley often votes republican. Southern states on the east coast often vote republican while heavily industried northern states vote democrat. The votes although red states or blue states are often split within 10% of 50/50 in most states with few exceptions. Popular votes throughout the country on the whole often split very close to 50/50.

So in the final analysis, States that swing Democrat more often have large urban populations and those that swing Republican are often less urbanized.