Testifying in Congress absolutely carries legal ramifications. It's just pretty hard to pin it so I agree with the "difficult" sentiment.
https://techcrunch.com/2018/04/11/is-zuckerberg-under-oath-c...
John M Poindexter was one who was convicted of lying to Congress: https://en.wikipedia.org/wiki/John_Poindexter#U.S._executive...