Billionaire investor Warren Buffett expounded on a number of subjects in an appearance on CNBC's "Squawk Box" on Monday.

Giving investors an idea of his commitment to the market, he said he bought stocks after the Sept. 11 terrorist attacks, and after the 1987 stock market crash. "The country is not going to go away," he said. "The country will grow in value over time."

The Berkshire Hathaway chairman and CEO said he bets on American business doing well over the long term, though he acknowledged that businesses have been "a bit softer" than they were four to five months ago.

"We're almost always a buyer of stocks," he said. "It's hard to think about many months when we weren't a net buyer of stocks."

The Oracle of Omaha also provided his views on everything from individual stocks — IBM, Dow Chemical, and Wells Fargo, just to name a few — to the presidential nomination race, to the privacy battle between the government and Apple two days after releasing his annual letter.

Here is a roundup of CNBC's Buffett interview:

We need a big mattress for money in Europe

Buffett said he's concerned about negative interest rates, now seen in Europe and Japan.

"We are doing something the world has never seen," he said. "We do not know how this movie plays out."

Apple vs FBI—Buffett says 'privacy has its limits'

He said national security matters should supersede privacy concerns in major issues.

"We live in a very, very, very dangerous world," he said. "If you were in the early days of September 2001 and you were receiving credible information that something was going to happen ... I think that in that case security trumps privacy."

Buffett: Buying IBM a mistake? Don't think so, but ...

Buffett said investing in IBM was the right decision, but it could turn out to be a mistake.

"We've owned stocks that we've lost money in," Buffett told CNBC. "If I'm wrong, you sell them out and take a big loss. We've done that on a few occasions with stocks and bonds over the years."

Buffett: Here's what I like about Bernie Sanders

He may be a Hillary Clinton supporter but he appreciates Sen. Bernie Sanders' speaking his mind.

"What I like about Bernie Sanders is he'll say exactly what he believes. He is not tailoring his message week by week. You'll find with some of the candidates that they shift around, or they don't answer the question. With Bernie, you know exactly what he thinks," Buffett said.

Still want more? Here's the full, uncorrected transcript from Buffett's 'Squawk Box' appearance.

— CNBC's Matthew Belvedere, Thomas DiChristopher and Terri Cullen contributed to this report.