It's hard to know what the current political measure of an impeachable action is. After reading this wikipedia a bit:
https://en.wikipedia.org/wiki/Impeac..._United_States

It's clear that Trump has already gotten away with far more than Andrew Johnson did.

Quote Originally Posted by wiki
Two of the articles against President Andrew Johnson were based on rude speech that reflected badly on the office: President Johnson had made "harangues" criticizing the Congress and questioning its legislative authority, refusing to follow laws, and diverting funds allocated in an army appropriations act,
Game's on us. This is clearly Trump's best troll, yet.
"Hey, Rudy. Wanna do everything on this list of things that other president got impeached for, but we get away with it?"

***
Turns out that while I know a bit about the process of impeachment, I now nothing about the reasons it happens.