Eh, what are you gonna do? You are overthinking it, comrade. Just try your best. It's okay to not be perfect and that the world isn't perfect. As long as you try to do what you can to make it better you are doing great. You are not a God, are you? So why do you insist on taking the sins if the world on your shoulders?

And how can you be useful? Comrade, the fact that the imperial core are imperialist parasite states only means that anti-imperialist work is more important! A successful anti-imperialist movement in your country could help prevent it from entering an imperialist war. It could change some of it's imperialist policies. The movement could help develop the productive forces of exploited nations. A strong proletarian movement with even a little internationalism could prevent a slide into more reactionary and violent social or haute bourgeois fascism, and ensure a tough but comfortable imperial decline for you, your loved ones, and vulnerable minorities in your country.

Ultimately, you are making the world system of imperialism about yourself. You are taking an economic and political fact, and using it to justify running with an emotional impulse. It is of course understandable to be distraught about the imperial lifestyle, it is in fact good to recognize the inherent parasitism! What is not good is reacting so strongly to it that it debilitates you politically. I think it is ultimately a form of liberalism to react in such a personal way, and would recommend you have a look at Combat Liberalism by Mao.