You will be unable to make an asylum claim in Canada if you enter it from the land border it shares with the United States.
This is because of the Safe Third Country Agreement, which states that refugee claimants are required to request refugee protection in the first safe country they arrive in, unless they qualify for an exception.
This means that if you arrive as a refugee to the US, your asylum claim must be made in the US, as it is the first safe country you will have arrived in.