What makes leftist parties unviable is the majority of the population disapproving of socialism.

People online vastly overestimate the actual effect of money on political results, naturally disregarding all the donations made to candidates that lose and ignoring races where the lesser funded candidates win.

If Americans wanted a leftist government, they’d vote for it, simple as that. And yet even in the most left leaning states and cities in the nation , leftist principles have failed to gain much electoral ground.

The CCP:

-- Put a million Uighurs in camps

-- Persecutes followers of pretty much all religions --- Muslims, Christians, Buddhists, Falun Gong, etc

-- Flat-out censors anything that offends them in the slightest

-- Puts whoever they want into detention with no kind of due process, from small-time activists to billionaires

-- Harvests the organs of (not previously dead) prisoners

-- Had drones peering into apartment windows during the latest COVID lockdown, broadcasting the literal message "control your soul's desire for freedom"

-- and of course is an autocracy in which Xi Jinping has absolute power

The USA is far from perfect but one thing we learned from Trump in 2016 and Bloomberg in 2020 is that money isn't everything in American politics. The parties do have major differences and bad actors can be held accountable.

I'm not American, but this equivalence that some people like to draw between the governments of China and the USA drives me crazy.

No it doesn't. Except for cancel culture (which isn't state run btw), you can say and think almost whatever you like in the USA so long as it isn't prejudiced or harassing. You are also not punished for starting other parties in the USA, since it's completely legal. Thus there are alternatives to the Democrats and Republicans. The First Past the Post system just means that that it's extremely unlikely that alternatives will ever challenge the biggest two. Other than that the American system is decidedly liberal and free.