the difference between extreme democrats and Republicans

Biden is not remotely extreme. The only reason he even won the 2020 primary is precisely that he’s not extreme, he’s the “safe” status quo candidate that was perceived as most likely to beat Trump. If it wasn’t for Trump, Bernie Sanders would’ve beaten Biden.

"Biden is not remotely extreme."
Some would argue that opening the border to allow in millions of likely democrat voters, is extreme. Or abandoning hundreds of Americans behind enemy lines to be butchered by the Taliban was extreme(ly stupid). And so on, and on and on

Illegal immigrants can’t vote. And given the backgrounds of many of them, assuming they’d likely vote democrat if they could is pretty baseless. Most I’ve met have been much more conservative than most citizens in their area.