Economically of course but i don't think you could Just take America alone. To get it done right you'd have to destroy their supporters as well while making them fight between each other and others to lessen the battlefield and put them in debt.
First I would have to set a plan in action that within 60- 70 years would give my elitist's power over all financial transactions. Along the way I would bankrupt my enemies replacing corporations and businesses with my own. I'd definitely have to take charge of all media to keep the simple minded occupied and out of the loop of whats really going on while i continued blaming everyone else for the worlds problems. After awhile, I'd begin keeping the government under my thumb and heavily indebted by making them fight wars that I would finance on both sides. Over time i would find ways to raise the price of EVERYTHING while keeping wages capped, bankrupt even more corporations and exert even more power.. Once the people had enough I would submit help but only enough to sustain them while weakening them further. Then from behind the scenes I would once again destroy everything they built putting an extreme amount of stress on the world economy before making them fight each other. Neighboring countries, allies and their whole society would be Bankrupted until only hope was left. Then i would step in as savior but on my conditions feeding the millions upon millions while rebuilding government. In the end it would be about 7 10th's of the world under one government having only one currency. What's left of the world would either be slaves nations or underground societies that I would find and crush.
Hope nobody's doing that already because I'm getting old and just started today.