Tom Lee: Ignore Greece—THIS is what really matters

Greece bit of a 'sideshow': Thomas Lee

The Greek debt drama is a "sideshow" for U.S. investors, who should be encouraged by signs of a stronger American economy, longtime stock market bull Thomas Lee said Tuesday.

"Greece isn't the systemic risk that it was three years ago," he told CNBC's "Squawk Box."

"Focus on U.S. fundamentals, which have been really good."

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Wall Street started the week with a rally, which marked the fourth gain in five sessions, and left the Nasdaq composite and small-cap Russell 2000 index at new highs. Based on Monday's close, the was just 0.6 percent from its record high, while the Dow Jones industrial average was 1.3 percent away.

"I know people are fearful about rising rates and Fed tightening and what it means. But at the end of the day, we're actually seeing reflation—the good kind of rising prices in the U.S. I think it's bullish for capital spending and bullish for housing," Lee said.

Those trends are going to lead to an upside earnings surprise later this year, he predicted. "I think this is going to look more like the early 1950s … [when] Fed tightening was really bullish for equities."

Another factor that should boost U.S. stocks, according to Lee, is a catch-up rally. He said the market here is due, after under-performing stocks in European and Japan.

He advised playing old tech, financials and housing-related stocks.

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Lee launched his own boutique equity research firm, Fundstrat Global Advisors, after leaving JPMorgan as chief equity strategist last year.