For anyone looking for evidence that boasts about “America First” — and the need for America to go-it-alone — are over, President Biden’s speech to the Munich Security Conference was meant as an opening argument.

“America is back, the trans-Atlantic alliance is back,” Mr. Biden declared. Trying to expunge the last four years without ever once naming his predecessor, Donald J. Trump, Mr. Biden said “we are not looking backward.”

And then he went on to offer a 15-minute ode to the power of alliances.

He talked about an America that was itself overcoming challenges to the democratic experiment.

“We have to prove that our model isn’t a relic of history,” he said, a clear reference to the critique that China and Russia have been helping to push. “We must demonstrate that democracies can still deliver for our people in this changed world. That is our galvanizing mission. Democracy doesn’t happen by accident. We have to defend it. Strengthen it. Renew it.”

In sharp contrast to Mr. Trump, who declined on several occasions to acknowledge the United States’ responsibilities under Article V of NATO to come to the aid of allies, he said “We will keep the faith” with the obligation. “An attack on one is an attack on all.”

But he also pressed Europe to think about challenges in a new way — one that differs from the Cold War, even if the two biggest adversaries were familiar from that period.

“We must prepare together for long-term strategic competition with China,” he said, naming “Cyberspace, artificial intelligence and biotechnology” as the new subjects of competition, which he said he welcomed. The West must again be setting the rules of how these technologies are used, he argued, rather than ceding those forums to Beijing.

And he argued for pushing back against Russia — he called Vladimir V. Putin only by his last name, with no title attached — mentioning in particular the need to respond to the SolarWinds attack that was aimed at federal and corporate computer networks. “Addressing Russian recklessness and hacking into computer networks in the United States and across Europe and the world has become critical to protect collective security.”