[zigman1]

That's interesting to hear that it is so relaxed in Europe. I work in EU at a multinational with offices all around the world, and within Europe, we are not legally allowed to enter the offices in other countries. The reason is simply that if there is a labor/work inspection (sorry, don't know the exact English expression) they can get a fine if I do not have a work order for a project abroad.

[eitally]

This is true in the US, too, but selectively and only really enforced in a meaningful way by a few states (including California). If you spend 30+ days in California for work reasons (visiting a employer's office would count, even if you're not on the clock when you do it) it triggers state income tax requirements. No fine, but equivalently unpleasant.