.gov was a bad idea.
.gov.us (or .gov.ca.us) is not.
Outside of obviously regional things. amazon.de and amazon.ca serve their purpose fairly well.
I would agree that the difference between ibm.com and ibm.org and ibm.net is impractical at best.
I don't see the need to have a distinction between amazon.de and amazon.ca. If Amazon wants to segment by country, they can do that on their own, not by offloading onto DNS.
Getting rid of also silly things like .co.uk would be great, but raise lots of uncomfortable questions. Ideally, DNS is would be nationally/politically blind, with the exception of government entities under .gov.*.{gTLD}
With no geographic-based TLDs, you introduce a need to disambiguate non-related brands which would have been perfectly distinguished by ccTLDs. Compare http://www.era.mk/ and http://www.era.pl/ - neither organization is controversial in its right to the TLD in its country, but one or both would have to settle for a disambiguation otherwise.