The Canadians that do not have work visa but have a base in the US cannot be in country for more than 180 days per year...so they can not practically live in the US. if you have a work visa, then you can take up full time residency. There should not be any restriction for other nationals working for CX. As for the Mexicans, they don't need visa, they just cross the border. Germans...well, I don't want to start a thread drift.