You will normally be asked which you prefer when reserving a room or when checking in. The fines for smoking in a prohibited public place tend to be high. Offenders will usually incur the considerable cost of cleaning any non-smoking motel room or vehicle. Smoking in a plane toilet is a very serious criminal offence due to the fire risk. Advertisements for cigarettes are now very rare in the USA and Canada.
Billboards clearly stating the health dangers associated with smoking are much more common.