They can and exercise a lot of discretion in not doing so. It has nothing to do with the legal authority, which they can also rationalize, feel free to come to

They can and exercise a lot of discretion in not doing so. It has nothing to do with the legal authority, which they can also rationalize, feel free to come to the US and appeal in court. The internet being administered by US corporations makes them easily compellable and any property they steward can be seized despite being for the benefit of foreign citizens and non-residents.