He also escalated his attacks on the press, pitting the news media against conservative values and suggesting he was going to take action soon to end what he described as a scourge of "fake news."
Speaking at the Conservative Political Action Conference, Trump vowed an economic revival spurred by new jobs and scaled back regulation. He insisted that his most prominent agenda items would be realized in short order. And he characterized in nationalist terms the "America first" theme of his presidency.
"Global cooperation, dealing with other countries, getting along with other countries is good, it's very important. But there is no such thing as a global anthem, a global currency or a global flag. This is the United States of America that I'm representing," Trump said to raucous applause at the conference, held at a hotel and convention center outside Washington.
"I'm not representing the globe," he said. "I'm representing your country."
Trump also said he is putting together a "massive budget request" to upgrade "all of the military."
"We will be substantially upgrading all of our military, all of our military. Offensive, defensive. Everything. Bigger and better and stronger than ever before. And hopefully we'll never have to use it. But nobody's going to mess with us, folks. Nobody," he said.
It was a return for Trump to the campaign speeches that propelled him into the White House, including chants of "lock her up" from the crowd, a reference to his former rival Hillary Clinton.
In his speech, Trump committed to aggressive action on creating jobs and heightening security, despite what he said were forces working to stymie his plans. He vowed new action to prevent terrorists from entering the US in a matter of days.
"Let me state this as clearly as I can: we are going to keep radical Islamic terrorists the hell out of our country," Trump said at CPAC. "We will not be deterred from this cause. And in a matter of days we will be taking brand new action to protect our people and keep America safe. You will see the action."
The White House is expected to unveil next week a revised order barring travel from certain Muslim-majority nations after an initial executive action was stalled in courts.
The President said that new jobs were starting to "pour back" into the country after declines in manufacturing, and suggested he was planning new efforts to remove Americans from welfare rolls and back into paying jobs.
"It's time for all Americans to get off of welfare and get back to work. You're going to love it!" Trump said.
It was a return for Trump to the same venue which sparked his political aspirations six years ago. Trump said on Friday that he arrived at his first CPAC address in 2011 with "very little notes and even less preparation."
"I loved the people, I love the commotion," Trump said of his first appearance. "When you have practically no notes and no preparation and everyone was thrilled, I said I like this business."
Back then, Trump was a brash billionaire with a popular reality television series. He appeared at the conference regularly in the ensuing years, though he was conspicuously absent last year, in the height of the Republican primary contests. Organizers said he wanted only to deliver a speech when they requested he participate in a question-and-answer session, but Trump said Friday that his positions during the campaign were "too controversial" for the conservative gathering.
His then-GOP rivals did attend, and mocked Trump for his absence. The episode illustrated some conservatives' deep apprehension about Trump, who had never previously held political office.
Trump sought to underscore his conservative credentials Friday, declaring work on his proposed border wall ahead of schedule and vowing to repeal the Affordable Care Act soon.
"As we speak today, immigration officials are finding the gang members, the drug dealers and the criminal aliens and throwing them the hell out of our country. And we will not let them back in," Trump said. "They're not coming back in folks."
And he delivered another screed against what he called "fake news," arguing the media was intrinsically at odds with conservative values.
"I called the fake news the enemy of the people and they are," Trump said, insisting that while he wasn't opposed to the media as a whole he would continue to chastise news agencies for stories he claims are false.
"They're very smart, they're very cunning," Trump said, to cheers. "There are some terrible dishonest people and they do a tremendous disservice to our country."
"It doesn't represent the people, it never will represent the people, and we're going to do something about it," Trump said of the media, without specifying what steps he might take to rectify the situation.
UPDATE: Trump's speech occurred Friday.