Selectively enforcing only the laws you want to is the key enabler of corruption.
You are just wrong.
America didn't even really have borders for most of it's existence, as the very idea of a Nation wasn't really a thing until into the 1800s.
We had a purposely pourous border with Mexico until relatively recently.
How many mexican immigrants do you happen to think live in Minneapolis?
There was significantly more inter ethnic strife in the US pre WW2 than most people seem to appreciate, much of it relating to if encountered (by whatever means) people should be settled/assimilated/rejected. There were riots/protests of this type in major cities at least between the civil war and the 1930s, and state policy reflected this, such as with the Chinese exclusion act which would hardly have been possible without a border.