The Pulisic rumor has been talked back a bit as it now sounds like he wants to stay at Chelsea. I'm not sure why he would so it could all be a bunch of BS, but either way, I don't think Pulisic at United makes any sense at all. He's clearly not a tactical replacement for Ronaldo in any shape or form. He's a winger which means for him to play, he either displaces Sancho and Rashford on the left (and Rashford likely becomes primarily a forward) or he displaces Antony on the right.
If he plays on the left, then there you're putting Rashford in a position that isn't his best and there are not enough games to go around to keep Sancho, Pulisic, Garnacho, and Elanga happy. Left doesn't make any sense at all.
Right makes a little more sense as really it's Antony at the moment at that's about it though Sancho, Rashford, etc. could play there...but they don't. And the reason why they don't is the same reason why Pulisic doesn't make sense there. ETH seems to prefer his wingers to cut inside with their dominant foot to allow space for attack fullbacks to run into. Pulisic is right footed and doesn't fit that mold.