Ultimately it is extremely simple to understand how the working class of the imperial core benefits from imperialism. Forget for a moment concepts such as value, exploitation or superprofits.
Do you, the westerner reading this, have access to more and higher quality stuff than someone in the Congo or in Honduras? Yes? There you go, you're benefiting from imperialism.
How does this come about? It's due to the export of finance capital.
What does finance capital do? It creates a political-legal structure of value transference through the use of various institutions (debt, agreements, treaties, etc.).
What do these structures do? They ensure that value generated by the labor in an imperialized country flows to the capitalist-imperialists in control of these financial structures.
But that's not going into my pockets, though? The value the capitalist-imperialists extract comes in the form of real commodities: coffee, cotton, minerals, bananas, oil.
Do you have access to any of these? Then you have access to imperial spoils.
That is the fundamental reality when you strip away the abstractions: Stuff flows from the imperial periphery to the grocery store you visit. Less stuff flows back to the periphery.
"but i produce stuff too! not my fault they can't afford it!"
When the things that you manufacture in your industrial job (cars, planes, ships, computers) -- made with raw materials coming in from the periphery -- are sold back to the periphery, it ensures that the worker in the periphery must toil more hours per item purchased than you do. Not only must they work the hours required to mine the minerals for the computer, they must then work additional hours at extremely low wages if they ever wish to buy the computer you assembled. How to save money when you're being paid less than it takes to put food on the table? You work even more, and your family works double duty to sustain you.
The things you make in your white-collar job (software, medical research, patents, media) are subsidized by the increased rate of exploitation in the periphery, and are likewise then sold to the periphery. You can do your job of producing intellectual property because someone somewhere mined the cobalt in your computer, grew the fruit you ate for breakfast and picked the cotton your clothes are made out of. And to top it all off, the intellectual property you export is essentially free to replicate! The only reason it's profitable is because of the coercive legal power finance capital wields, of the superstructural institutions it props up to enforce concepts such as "intellectual property."
So why doesn't the periphery simply ignore these bad deals, unadvantageous laws and sketchy treaties?
How do you stop people from breaking legal agreements? You send the cops after them. That's what the US military is.
"ok so should i just feel bad and keep doing what i'm doing or...?"
Two things are true simultaneously: You benefit from imperialist exploitation, and it is also in your own best interest to bring an end to imperialism.
See, imperialism is inherently unstable just as capitalism in general is. Why is the US currently lashing out in seemingly irrational warfare, both armed and economic? Why are social democracies in Europe dismantling their welfare systems and increasing military spending? Why are conservatism, the far-right and outright fascism on the rise? It's because of the decline of imperialism: just as the rate of profit falls with the mechanization of domestic industry, so does the rate of imperial superprofit fall when exploited countries, due to slow but steady industrial development, gain the capacity to contest and break free from the monopolies of extraction propped up by the imperialists. To bring profitability back, to discipline anyone who would break free, the imperialists become nakedly violent and coercive. Once hiding behind banks and treaties is no longer enough, they become mobsters and pirates toward the rest of the world.
Fascism is imperialism turned inward. When the exploitation of the periphery is no longer enough to maintain profitability, imperialists lash out abroad, and invariably turn their attention toward their domestic working class too. Socialized healthcare, cultural amenities and welfare benefits exist as a class compromise. "We give you basic stability and necessities, and you don't overthrow the government" is the deal. But when the capitalist class can no longer maintain this compromise, when they must restore profitability at all costs, the compromise must be dismantled. They cannot let themselves become unprofitable -- this is not because of greed, it's because the system of capitalism literally does not work without self-expanding value, without profit.
What does a working class whose welfare state gets gutted do? They start getting a bit rowdy, they start looking for alternatives, they start getting a bit socialist. What is the response to this by the capitalists, then? They can no longer pacify the workers with welfare and treats, so they use violence. Fascism is let loose to discipline the working class. Fascism is capitalism's self defense against socialism.
To be anti-imperialist is to be anti-fascist. To be a communist is to be the enemy of fascists.