Make all Internet crimes a Federal offense ?

Tampering with the US Postal Service in any way is a Federal offense, why not make tampering with Internet communications the same ?

It's too broad of a scope and would lead to more selective prosecution. Laws should be specific and unambiguous.

It works for the Postal Service though, and other than the mode of transport the Postal Service and Internet work pretty much the same.

I really don't see a similarity between the two. Besides, some FCC laws, which are federal, already cover portions of internet communication, even though the internet is not federally owned, as is, the postal service. The problem with internet laws is that law makers don't understand the technology which leads to mistakes.

They both transmit messages from point A to point B. One uses paper, the other uses electricity. What's the difference ?

The paper is tangible and the electricity is not. Going back to your original post, the phrase, "in any way" is too vague when applied to an electrical communication. It's even to vague for the postal laws. Laws have to be specific.

I will believe that electricity is not tangible when someone who has just touched the bare end of a live high-voltage powerline to their tongue tells me it's not.

I agree "in any way" is a little too vague. Rules are like wooden ducks, you have to start with a big ole log and whittle them down to as near perfection as possible.

I guess it comes down to translating what exactly about tampering with US mail is Federal, and translating that to Internet communications.

That translation will take a lot of time but it's all part of the whittling that you mentioned.