Investors focusing only on U.S. stocks and the Federal Reserve may be missing the broader picture regarding financial markets, especially what's going on with Brazil's Petrobras, CNBC's Jim Cramer said Monday.

He noted that the semipublic oil behemoth's 10-year bonds were yielding 10.5 percent, a level which he said is "unsustainable."

"This is the world's No. 1 problem ... right now because it has so much debt and people aren't talking about it," Cramer said on "Squawk on the Street."