Before the creation of the Magical Congress of the United States of America in 1693 there existed no unified Wizarding government in the US to interact with the No-Maj government. Individual wizards were keen to remain hidden due to the likelihood of persecution by Puritan fundamentalists.
It would appear that after the creation of the MACUSA, their first priority was to deal with the Scourer threat, something that would have been made more difficult had more No-Maj's been aware of the existence of the Wizarding world.
Perhaps the most significant effect of Salem was the creation of the
Magical Congress of the United States of America in 1693, pre-dating
the No-Maj version by around a century. Known to all American witches
and wizards by the abbreviation MACUSA (commonly pronounced as: Mah –
cooz – ah), it was the first time that the North American wizarding
community came together to create laws for themselves, effectively
establishing a magical-world-within-a-No-Maj-world such as existed in
most other countries. MACUSA’s first task was to put on trial the
Scourers who had betrayed their own kind. Those convicted of murder,
of wizard-trafficking, torture and all other manners of cruelty were
executed for their crimes.
Several of the most notorious Scourers eluded justice. With
international warrants out for their arrest, they vanished permanently
into the No-Maj community. Some of them married No-Majs and founded
families where magical children appear to have been winnowed out in
favour of non-magical offspring, to maintain the Scourer’s cover. The
vengeful Scourers, cast out from their people, passed on to their
descendants an absolute conviction that magic was real, and the belief
that witches and wizards ought to be exterminated wherever they were
History of Magic in North America: Seventeenth Century and Beyond
The article on Pottermore titled Rappaport's Law contains a great deal of relevant additional information. In short, the decision to completely withdraw from contact (at any level) with No-Maj's was driven by the indiscretion of a prominent witch. She exposed the wizarding world to the descendant of a Scourer (a wizard mercenary who had married a muggle) who then used this knowledge to persecute wizards at their supposed secret locations.
Rappaport’s Law further entrenched the major cultural difference
between the American wizarding community and that of Europe. In the
Old World, there had always been a degree of covert cooperation and
communication between No-Maj governments and their magical
counterparts. In America, MACUSA acted totally independently of the
No-Maj government. In Europe, witches and wizards married and were
friends with No-Majs; in America, No-Majs were increasingly regarded
as the enemy. In short, Rappaport’s Law drove the American wizarding
community, already dealing with an unusually suspicious No-Maj
population, still deeper underground.
Note also that this law came on the heels of censure from the International Confederation of Wizards, described as a "humiliation".