Trump's loyalty is already compromised, no matter what the Senate investigation says. Foreign nations will not risk sharing intel with the US for fear of it being passed to their enemies (see Israel today, Eastern Europe soon). This greatly reduces the American intelligence community's ability to prevent acts of terrorism; they won't be flying blind, exactly, but there's always the chance that something slips through the cracks. Trump makes those cracks much, much wider.
The worst part is that when something inevitably does happen, Trump can still say "Told ya these intelligence agencies were awful!"
