Whether all of the allegations about Trump and Russia are true, or only some are true, or even if all all false, these allegations are going to hang over every foreign policy decision of the Trump Administration. If Trump does something that Russia likes, a substantial number of people will assume he only did it because he is a Russian puppet. If he does something that Russia does not like, that decision is going to be viewed as an effort of Trump to rebut the Russian puppet allegation. The question of how much Trump is controlled by Russia is going to be the frame to evaluate every foreign policy move he makes when he is in office. It will sap the strength of any claim Trump makes that he is prioritizing American interests.
That's what Trump gets for his knee-jerk rejection of the hacking allegations, his refusal to release tax and other financial information to rebut rumors of Russian financial ties, etc. Because we don't know whether any of these allegations are true, we can't say whether Trump had any hand in creating those problems in the first place. But Trump's recent actions have definitely made the problem with his own foreign policy credibility a lot worse.