
Naval invasions are a lot more difficult, armored units aren’t easily transportable, and you still need good beaches as well. Lacking the hard power of an armored push makes assaults difficult in general, soft power can only get you so far.
Controlling the Panama Canal is a crucial lynchpin though as it allows you to easily reinforce a navy on one side with the other without going all the way down past Tierra Del Fuego.
I think he might have had better success if he painted the crosswalks to the same specifications as the ones the city uses.
If it blends in with all the other crosswalks, nobody will likely notice, at least until it gets repaved and the lack of documentation would be written off as some sort of administrative error.