And such spending cuts must start immediately as the price of getting GOP conservatives to cast a painful vote to increase the government's ability to borrow to pay its bills this spring, Ryan said.
"Our nation is approaching a tipping point. We are at a moment, where if government's growth is left unchecked and unchallenged, America's best century will be considered our past century," Ryan said in televised remarks.
"The days of business as usual must come to an end. We hold to a couple of simple convictions: Endless borrowing is not a strategy; spending cuts have to come first," Ryan added.
Ryan is the point man in the new House GOP majority's drive to rein in spending and bring the budget closer to balance. Tuesday's speech was the highest profile assignment yet for a wonky former congressional staff aide who has evolved into one of his party's brightest stars.
Ryan is best known for a controversial budget plan brimming with politically unpopular ideas like gradually turning Medicare into a voucher program, curbing Social Security benefits and allowing younger workers to divert Social Security taxes into private accounts. He says such tough steps are needed, given intractable budget deficits that threaten America's prosperity.
On Tuesday, Ryan, who often peppers his speeches with straight talk about the need for painful cost curbs to benefit programs like Medicare, Medicaid and Social Security, did not offer such "tough love."
Ryan's plan, the "Roadmap for America," is so politically toxic that GOP campaign operatives urged candidates to shy away from it. Democrats went on the attack as soon as they heard Ryan was to deliver Tuesday's GOP response.
"Paul Ryan owes it to the national audience tonight to explain why he wants to privatize Social Security and Medicare," Sen. Chuck Schumer, D-N.Y., said.
Speaking from a budget panel hearing room that will be ground zero in the upcoming battle over cutting spending, Ryan echoed familiar GOP arguments.
"We need to reclaim our American system of limited government, low taxes, reasonable regulations and sound money, which has blessed us with unprecedented prosperity," Ryan said. "And it has done more to help the poor than any other economic system ever designed."
Ryan's sentiments were repeated by numerous Republicans across the Capitol, who said Obama's proposal for a five-year freeze on the operating budgets passed by Congress each year for domestic Cabinet agencies doesn't go far enough.
They are also deeply skeptical of his plan for investments in education, infrastructure, and research and development.
"At a time when the Treasury secretary is begging Congress to raise the debt limit, a 'freeze' is simply inadequate," House Speaker John Boehner, R-Ohio, said.
Instead of deficit reduction, President Obama has put a forward a plan for deficit preservation," said Sen. Jeff Sessions, R-Ala., the top Republican on the Senate Budget Committee. "The president must provide vision and leadership. But tonight we saw timidity and denial. His plan did not rise to the moment or to the challenges we face."
Ryan acknowledged that there's plenty of blame to go around.
"Our debt is the product of acts by many presidents and many Congresses over many years. No one person or party is responsible for it. There is no doubt the president came into office facing a severe fiscal and economic situation," Ryan said. "Unfortunately, instead of restoring the fundamentals of economic growth, he engaged in a stimulus spending spree that not only failed to deliver on its promise to create jobs, but also plunged us even deeper into debt."
In an unusual move, tea party favorite Michele Bachmann, R-Minn., followed Ryan's response with high profile speech of her own. It was originally aimed just at tea party activists but was also carried live by CNN.
"After the $700 billion bailout, the trillion-dollar stimulus and the massive budget bill with over 9,000 earmarks, many of you implored Washington to please stop spending money we don't have," Bachmann said. "But, instead of cutting, we saw an unprecedented explosion of government spending and debt. It was unlike anything we have seen before."