This is an extremely simplistic view of the relationship between labor and capital.

First, this is not ultraleft. The ultraleft position is that all major governments (including the USSR, China and other AES) are actually bourgeois and imperialist and their people suffer from the same exploitation indistinguishable from those who are exploited in the imperial core, so their solution is that all leftists have to perform revolutionary defeatism within their own country (again, including the USSR, China and other AES) in order to overthrow their respective bourgeois regimes and come together internationally to enact communism on a global scale.

And as I have said, the comment you posted is also a very simplistic take on the matter.

We have to look at this from the perspective of revolutionary potential, in other words: does the working class in the Imperial Core have more, less or equal revolutionary potential as the working class in the Global South?

To dissect this question, we need to understand how the global economy works post-1971, after the vast export of their industrial capacity to the rest of the Global South while the US empire sustains itself as a global debtor (which is fundamentally different from the British empire, which was a global creditor).

The neoliberalized American economy since the 1970s has been propped up mostly by the so-called FIRE sector (Finance, Insurance, and Real Estate - a terminology coined by the economist Michael Hudson) which are essentially non-productive sectors that do not produce real goods and services. This is a prominent feature of finance capitalism devouring industrial capitalism:

The strength of its currency is derived from real estate ownership (land value), stocks and bonds market, intellectual property rights and licensing, financial derivatives etc. Now, you might think all these are virtual and therefore the US dollar is worthless. But no, this is what the world (held under the gunpoint by the US empire) has decided to calculate their GDP and currency exchange rate, which then allows the US to wreck other economies in the Global South using the strength of its currency, maintaining dominance over them and essentially extorting free lunches from all over the world, as most of the real goods and services today are produced by the Global South countries.

In other words, the financial empire is more like a landlord who does not have to work for a single day but can get everything he wants simply through extracting rent and concession. The US empire is doing this on a global scale against other countries.

While the Imperial Core enjoys the benefits of cheap goods and services from the Global South, this does not mean that their working class truly benefits from it. Instead, their exploitation became a form of debt slavery. Wages are kept low so workers have to borrow money to sustain themselves, which transforms their class character into one of debtor.

This kind of financialized capitalism means that unlike the late 19th and early-mid 20th centry, which was dominated by industrial capital, the working class in the Imperial Core today has their labor tied to debt (mortgage, rent, credit cards, student loans, medical bills etc.) rather than to industrial productivity, which was a key argument from Marx that proletariat is a uniquely revolutionary class because being freed from the land under the feudal arrangement, the labor performed by the proletariat is now directly tied to industrial profit under capitalism. The capitalists had to rely on labor to compete with other capitalists in order to make profit.

It has been described that the Imperial Core today under finance capitalism is more like a neo-feudal society rather than the industrial capitalism of the previous centuries. And this is largely true: just like the serfs in the feudal era, whose labor was tied to their land, the working class in the Imperial Core today work bullshit jobs to earn money to pay off their debt, which is what was necessary to survive in the first place. The manufacturing and service sectors pale in comparison to the FIRE sector, as much has already been exported to the rest of the Global South (and especially against China).

I am already writing too long but to conclude very quickly: the working class in the Imperial Core does have diminished revolutionary potential, which means that not only do they have to fight for better working conditions etc., but also the defeat of the non-productive FIRE sectors within their own countries in order to free themselves and the world of debt slavery. It is more akin the transition from feudalism to industrial capitalism, but in reverse. And only then, will they have the true potential to seize the means of production.

In other words, working class in the Imperial Core cannot simply organize just for improving the benefits of their own, but also need to incorporate anti-imperialism into their core struggles (which includes performing revolutionary defeatism of their own imperialist government) in order to defeat finance capitalism (which is rooted in the Imperial Core), which would then allow the socialist movements across the Global South to rise up against their bourgeois regimes, and by doing so advancing socialism across the world.

EDIT: can’t believe I forgot to say about the Global South. The working class of the Global South today suffers from the opposite problem: a left wing government (revolutionary or democratically elected) is immediately wrecked by sanctions, currency depreciation, burdening debt overhead from both currency depreciation and capital flight, endless coups, economic hardship etc.

So, the fundamental nature of struggles between working class in the Imperial Core and the Global South is different, YET they are tied together by the principal contradiction of anti-imperialism. According to this admittedly shallow and underdeveloped understanding of the world, countering imperialism (whose main instrument is finance capital i.e. currency) would simultaneously disentangle the contradictions of BOTH the working class struggles of the Imperial Core and the Global South, and opening up the spaces for further revolutionary struggle against Capital. Once again Mao’s On Contradiction could prove very useful in the analysis here.