Oh, laugh about trump, he's the head of a country and should either know better or listen to his advisors. I was mostly referring to average people.
About the surface survival ... that's actually a thing.
My (granted, superficial) dive into the literature has provided no exact time frames of how long the virus survives on surfaces, but it can easily be hours to days. There's a paper in which they checked where a patient left virus particles.
SARS-CoV-2 needs the ACE2 receptor, which is found a lot on the surface of cells in the respiratory tract (a review paper on that), so the general consensus is that it needs to somehow enter that (nose, mouth). However, I need to repeat that we don't know everything yet, so I wouldn't 100% rely on that.
Bottom line: Completely changing your clothes after shopping might be overkill. Touching groceries and packages might actually be risky, but I honestly don't have the patience to sanitise everything I buy. I try to minimise the number of things I touch outside, try not to come too close to people, and sanitise my hands if I have to touch something.