I am in no way suggesting that US Democrats have broader support.

I am stating that the US Republicans do not have the support of "half of the US"; either by half of total population, half of eligable voters, or half of registered voters.

US Independents should have stronger support but that's not really going to put much of a dent in what's iteratively evolved to become a two party bicameral political system thanks to the shortcomings of repeated "First past the post" voting.

What was a bright idea hundreds of years ago hasn't scaled well and converged to unrepresentative gerentopoly.