How will my Yemen nationality impact my EB-5 application if I am a dependent of my Vietnamese wife?

A travel ban on citizens of Yemen continues. This is governed by Proclamation 9645. Unfortunately, entry as an immigrant is suspended and entry is suspended for non-immigrants on business (B-1), tourist (B-2), and business/tourist (B-1/B-2) visas; however, you might be eligible to enter under other types of non-immigrant visas that are not suspended.

As long as you are married before she obtains her conditional green card, you can immigrate with her. Otherwise, she will have to petition for you in the F-2A family preference category. Your Yemen nationality may actually help because the country of chargeability for immigrant visa number/visa bulletin purposes is the country of birth of the principal applicant or the country of birth of the spouse. Vietnam is subject to a visa number cut-off date (Sept. 1, 2017) while Yemen is not because it is considered in the "rest of the world" category, excluding China, India, Mexico, the Philippines. As for remaining in Canada for an extended period of time, you can apply for a U.S. re-entry permit, which is valid for two years if you need to remain outside of the United States that long, or you can maintain the intention to permanently reside in the United States and not be absent from the United States for more than six months on any given trip abroad/to Canada.

She can cross-charge to Yemen if you are married.

You can immigrate with your spouse, if you are married, based on your spouse''s country of birth.