Lots of issues:
Safety certification (UL/CSA/CE Mark aspects/...) This is needed both for the power supply and the device itself
Environmental hazardous substance bans
Recycling fees (like in California)
Actual recycling (like in Europe)
Radio certification, both WiFi and cell frequencies and non-interference
Warranty coverage/local repair centers and terms which vary by country
How is voice being done with an LTE-only device - VoLTE, Google Voice?
Which LTE frequencies will be covered?
Sales tax/VAT - some countries allow importer to pay this, others require a single distributor in each country to pay this. Otherwise your device may get stuck in customs.
Export/import classification for a number of countries - what happens if someone from North Korea tries to buy one - there is probably enough US content to prohibit it.
While power supplies can adapt to different voltage/frequency, different plugs are needed for each country. The power supplies are typically the most sensitive for safety regulations.
Non-uniformity of country laws - China prohibits full disk encryption - what unique laws may affect product?
Charging only an extra $30 to ship outside US/Europe makes me think Canonical doesn't understand how much getting certifications from multiple countries/carriers will cost, or will leave the risk of not being certified to the purchaser.