None of Flynn's wrong-doings will have much political impact until congressional Republicans decide to turn on Trump. Right now, they are mostly holding steady in their nothing-to-see-here approach, but cracks are starting to show in the facade. Yesterday Paul Ryan stated that people (whoever could this be?) who are extremely careless with classified info should be denied access to it, presumably in response to Trump's flagrant open-air national security dealings at Mar-a-Lago.
When will they turn on Trump? My guess is that they are waiting for the mountain of evidence of collusion with Russia to build and turn from circumstantial to confirmed. Most Republicans are smart enough to know that they do NOT want to go down in history as patsies in a cover-up of a foreign governments' intrusion in the US, and that's where this train is headed, so we know they'll need to get off this ride eventually.
Flynn was the first instance of confirmed collusion, more will certainly come. When hard proof drops that Trump knew and was involved -- and, at this point, it seems impossible that he didn't know (and if he truly didn't know that is a problem in its own right) -- they'll turn on him quickly, and en masse.