Yes, Canadian citizens are allowed to work in the U.S. as long as they have a work visa. Canadian citizens have the following work visa options:
      TN visa for Nafta professionals
      L1 visa
      H1-B visa
      O1 visa
Each visa covers a different category of workers and has its own criteria for eligibility. As a Canadian citizen seeking work in the U.S., the visa that you should apply for will depend on your type of employment, your credentials, and the length you wish to stay in the U.S., among other factors.

TN visas are a popular choice for Canadian citizens seeking work in the U.S. because they have minimal eligibility requirements and are relatively easy for Canadians to obtain. Also, TN visas last three years and can be renewed easily.
Eligibility for Nafta Professionals
   To qualify for a TN visa, applicants must meet the following eligibility requirements:
   Be a Canadian or Mexican citizen
   Work in a field that is on the Nafta list of approved professions
   Work in a position that can only be filled by a Nafta professional
   Work in a prearranged position for an employer; self-employment is not permitted
    Have qualifications for the position, including education or employment history
Requirements for Canadian Citizens
Under TN worker classification, Canadian citizens do not actually need a visa to enter and work in the U.S. While Canadian TN workers can apply for a formal visa with the United States Customs and Immigration Service (USCIS), Canadian citizens can also simply apply for TN nonimmigrant status when they first enter the country.

Applying for a TN visa with the USCIS can take a couple of months to process and is more expensive than applying at a port of entry. Also, applying at a port of entry gets you a quick decision on TN status, so if you get denied you know why immediately.

Canadians must submit the following documents to the U.S. Customs and Border Patrol at a legal port of entry to establish eligibility for        TN nonimmigrant status:
  Proof of citizenship
  A letter from your American employer describing the position that you have been hired for, how long you are staying, and your               qualifications for the position
  Documents that prove your credentials
  Payment of relevant entry fees
U.S. Citizenship and Immigration Services: TN Visa

The L1 visa allows companies to temporarily transfer a foreign employee to work in the U.S. at an American branch of the same company. This visa is reserved for workers who are classified as managerial or executive, or who work in a “specialized knowledge” capacity. The L1 visa is a “dual intent” visa, so L1 visa holders do not have to maintain a foreign residence while in the U.S.
To qualify for an L1 visa, you must:
     Have worked outside the U.S. full-time for one of the past three years
     Have worked for a qualified organization outside the U.S. in a managerial, executive, or “special knowledge” capacity
     Have been transferred by your employer to an American-based branch, affiliate or subsidiary of the employer
 U.S. Citizenship and Immigration Services: L1A Visa
 U.S. Citizenship and Immigration Services: L1B Visa

H1B visas are among the most popular and well known of U.S. work visas, and can be used by Canadians to work in the U.S. The H1B visa is for individuals with at least a Bachelor’s degree who seek work in the U.S. in a “specialty occupation.” Specialty occupations are occupations that require a Bachelor’s degree or higher and includes fields like architecture, finance, engineering, and accounting.
To qualify for an H1B visa, Canadian citizens must:
    Have a job offer from a U.S. employer who will act as a sponsor for the visa
    Be working in a “specialty occupation”
    Get paid the minimum wage in the state that you will reside
Obtaining an H1B visa requires entering and being selected in the H1B visa lottery. However, Canadian citizens with an advanced degree can apply for the U.S. Master’s Cap Visa. The Master’s Cap category has its own pool in the lottery, and applicants not selected in the Master’s Cap pool are then entered into the general pool, so they have a better chance of getting selected
U.S. Citizenship and Immigration Services: H1B Visa

The O1 visa lets individuals with “extraordinary skills” in their fieldwork in the United States for up to 3 years. There are a number of ways that applicants can prove their skills, including:
    Winning international prizes, grants, or awards
    Being a member of a prestigious national or civic organization
    Having work featured in major national or international media
    There are two different types of O1 visa, the O1A, and the O1B. The O1A visa is for individuals with exceptional skills and recognition in certain fields like science, technology, finance, education, or athletics. The O1B visa is for individuals with exceptional abilities in the arts and motion pictures.
U.S. Citizenship and Immigration Services: O1 Visa

Getting a work visa in the U.S. is easier for Canadians than almost any other nationality, and you have several options to choose from. However, most of these options require a job offer and proof of credentials, and some require more substantial credentials than others. The TN visa is the simplest and most accessible option, while the H1B and O1 visa are for highly accomplished individuals and the L1 for individuals in a specific circumstance.