Damals:
The idea that the two coexisted for over 200 years is an exaggeration bordering on an outright falsehood. The original Copyright Act of 1790 applied only to "maps, charts and books" and specifically covered "printing, reprinting, publishing and vending." Oh yeah, and you had to register the work. And the copyright only lasted for 14 years, renewable for another 14 years, if the copyright holder chose to do so. Oh, and we shouldn't forget that it really was only a violation if you printed the entire work. You could copy large segments of the work. So, basically, copyright covered a very small number of works, in very limited ways, for a fairly limited period of time. And, it's probably also worth noting that, at that time, the most successful US publishers weren't printing books by Americans, but rather books from English authors, which were considered public domain under US law.
Heute:
Compare that to today. Since 1978, copyright in the US now applies to everything new and creative the instant it is in fixed form. That means pretty much everything, from that email you just sent your boss to the lovey-dovey note you direct messaged your significant other on Facebook, is technically covered by copyright. No registration necessary. It covers way more that maps, charts and books. It goes way beyond just printing, reprinting, publishing and vending (all ostensibly commercial activity) to any form of reproduction, distribution, performance or creation of derivative works. And it no longer just applies to the entire work, but also to tiny snippets of the work, with the marginal and extremely limited exceptions put forth by fair use – which the courts have (incorrectly, mind you) stated is merely a "defense" rather than a "right." Oh, and it lasts the life of the author, plus another seventy years. And, yes, it covers foreign works as well.
These two things are not the same. At all.
Yep. Ähnliches lässt sich über die Entwicklung des deutschen Urheberrechts sagen.