I'd include: have really good walls. Those saved their bacon time after time.
It seems similar in business cases.
I love all the giant old stone walls in Istanbul, the place is filthy with them. The people are totally used to it too - it's trippy to see schools and homes built around centuries-old ramparts.
For example, Google has built up its own wall by making practical extremely large computing platform. That's a big wall for them to deter competitors. Apple focus on user experience and that is a big wall for them to fend off copycats.
If U.S. has to build a big wall. The wall has to be something that make U.S. an aspiration for those enemies of our enemies, such as rebel students in Tehran or Beijing.