State the actual known arrangement and explain what remains undecided.
Avoid presenting a placeholder as an established fact
Ask the employer for an accurate account of the location terms and update material facts as they become known. An address should not be described as the assigned worksite merely because it makes the document appear complete.
Build the letter around facts the employer can presently confirm: the employing entity, professional duties, compensation, temporary period, supervision, and the method for selecting a site. Mark a location as pending when it truly is; a convenient placeholder can create a credibility problem when schedules or contracts show otherwise. The applicant should also assemble proof of Canadian or Mexican citizenship and the evidence demanded by the chosen USMCA profession, including a reliable credential evaluation where applicable. Prearranged work must remain distinct from prohibited US self-employment. A Canadian may generally present the coherent package at a port of entry, while the employer may instead use Form I-129.
Hypothetical example: A land surveyor living near Saint-David-de-Falardeau is hired for projects allocated after contract award. His support letter can explain the allocation process and attach the signed offer, current project description, licence or education records, and truthful correspondence about location. Inserting the employer’s headquarters as his settled worksite would conflict with the unfinished assignment record and should be avoided.