Yeah, although it used to be that if you were legal to enter the US you actually could do it anywhere, just report to the local officials as soon as practical. That's still how ships work, you have to enter a country's territorial waters before you can speak to an official.

Neither the US nor Canada does that now, effectively slicing the Pacific Coast Trail at the border. And now we have the scumbags for no good reason blocking off access to the southern terminus of the Continental Divide Trail. That fence isn't going to stop someone trying to sneak into the country!