Yes, it is the country code. But the question still stands, is it possible to remove it? Scott isn't the only that doesn't have the country on numbers in the previous contact list. This causes duplicate phone number listings for the contacts with their number on Facebook. This was issue for me when I tried to have Siri call someone. Since their phone number was listed a second time with the country code, Siri asked which number I wanted to call them on.
It seems that the only way to currently correct the problem is to add the "+1" to all my my iCloud contacts. It's a bit of a chore, but I tested it and I no longer have Siri asking me which of two basically identical phone numbers do I want to use to send a text or make a phone call.
For those that sync iCloud with Outlook, there is a quick fix for it. Opening up the contact information on a PC, double clicking on the phone number pulls up a built in phone check which automaticall adds the "+1" on the number. My country/region box is default to the United States. After that, clicking OK, and then Save & Close and move on to the next. It's still a task, but a lot faster than doing it all on the iPhone itself.
I checked in the Address Book app on my MBP but couldn't find as quick of a fix on it so the OS X users out there will have to manually do it all I suppose.