Oh, so you think taxing the snot out of corporations and the rich will work. It won't. They'll leave. They'll go somewhere else. People and corporate leaders don't mind paying reasonable taxes but won't put up with being robbed.
Both parties created budget deficits, but that isn't the biggest problem with the federal budget. About 66%, two-thirds of it is inviolate. That is, the spending is mandatory, budget increases are usually tied to inflation and automatic, and there is no way to stop that. About 75% of that sort of thing is social-welfare spending so it doesn't really generate any economic growth as a result.
Both parties are guilty of using the budget to get political gain, so get off your high horse that it is somehow just the Republicans you fucking retard.
Government spending mostly doesn't grow the economy. Small portions of it may, but that's miniscule to the overall waste in government spending.
Credit gets downgraded when there's too much government spending and not enough economic growth. The economy isn't growing very fast at the moment, particularly when you take inflation rates into account.