In the U.S.A., it's illegal and a criminal offense just to endeavor, try or attempt to obstruct justice. One doesn't actually have to obstruct justice. An attempt alone is a criminal offense. 

The information from Comey's private meeting with Trump is a case of he said he said. 

But Trump later fired Comey who was leading the FBI investigation into the Trump campaign/Russia connection and 2 days later Trump himself said it was because of "this Russia thing". 

That certainly seems like Trump was trying to interfere with an FBI investigation and was trying to obstruct justice, which is a criminal offense. 

Just trying or attempting to obstruct justice is a criminal offense and the evidence Trump was trying to obstruct justice is mounting.