But that is already an issue - whether or not you have a .com domain name. The domain name is just an asset and the government routinely seizes assets when filing criminal charges.
The US government has always had dominion over .coms (and .nets). Verisign manages .com's through a contract with the US Department of Commerce. That's where they get there authority.
If .com domains weren't considered to be USA based though then a USA citizen would be the one that was being charged for breaking the law wouldn't they?
Flip it around. Suppose someone is selling online under a Somali .so domain rather than a .com; the law should operate in the same way as long as the web servers themselves aren't located in USA.
Isn't it the assumption that any transaction with a .com is essentially under the purview of USA law that is at issue?
This just emphasises the need for .com to be considered neutral territory. It's only a redirection mechanism - USA can have and apply their laws to .co.us and of course any server that is based in USA.
It's not transactions with the .com that's at issue. It's the fact that a company operating a business the government considers illegal is making money in the US and moving it overseas.
It's all about the money. Not .COMs.
Running a gambling site on an .so domain and hosting the servers overseas while profiting in the US will still get you indicted. The government might not have the authority to shut off your internet presence but I'm sure they could turn off finances in the US. And certainly make travel to certain countries an issue.