Of course the UK would vote Democrat by a landslide in *this* election and FWIW the polling has confirmed as much. Indeed, this would also be true were we split into our 4 consitituent "parts" statewise (little doubt that "even" NI would go heavily Biden, and England would be scarcely less emphatic than Scotland)
How we might vote if the GOP offering was more in their "traditional" mainstream (leaving aside the question of when, if ever, that might again happen) is maybe a more interesting question however.
It's doubtful Britain would be much better for the GOP with a more generic candidate unless said person was of the Charlie Baker mould but of course such a person would never be able to win a Republican primary. The issues that animate the GOP base nowadays are the kind of things that would play really badly with the British electorate (including the majority Tory voters). For example:
-Britain is extremely secular, more so than even the likes of Vermont. The GOPs pandering to evangelical voters and religious moralising would go down like a lead balloon over here.
-The British public is extremely anti-guns. The GOPs obsession with allowing weapons of war on the streets would cost them many votes.
-The British public doesn't really care about the wedge social issues (abortion, gay rights, trans rights etc.) that the GOP has used to win elections over the past several decades, provided they don't perceive them to be affecting them directly. Whilst the Tories obviously contain a faction of people who do tend to agree with this social outlook, the party as a whole is smart enough not to make these a major feature of their campaigns as it would be a sure-fire losing strategy.
The exception to all of these would be xenophobic dog whistling, though the GOP has gone far beyond dog whistling at this point and are opening shouting it from the rooftops. This would probably be too far for the British electorate.
Honestly I think Trump 2016 may have put in the best performance in Britain of any GOP nominee since H.W. in 1988 (or possibly 1992). This is because he would have likely made inroads into some of the white working class, lower middle class secular communities in places like the Midlands just how he did in the New England, upstate New York, south Jersey etc. He would indeed be heading for an utterly horrible landslide defeat in 2020 though.
A more interesting question though would be what the US political map would look like with British Parties (I imagine there is a thread for this somewhere). I'm pretty sure Johnson would have absolutely annihilated Corbyn, quite possibly nearing a 50 state sweep (yes even including the likes of California and New York) as Corbyn's politics and personality would be a uniquely terrible fit for the USA. I'm sure a more 'typical' Labour politician such as Miliband or Starmer would be much more competitive though, and I suspect they would perform better in ex-industrial areas than the Dems currently do but worse in suburbs.
