To take it? Absolutely not. To buy it from another country? Yes.
Of course, to buy it from another country, but for what purpose?
To incorporate it into the United States of America. First as a territory, then as a state. Once statehood is achieved, all rules, limits and obligations become limited to ONLY what the Constitution allows the fed gov.
The fed gov originally taking possession of the land by purchase, rather than conquest, makes no difference what-so-ever.
The fed gov is limited by The Constitution and any acts, actions or possessions that lay outside the restraints placed upon the fed gov by The Constitution are illegal and illegitimate.
It is not only our right, but our duty as citizens to force the fed gov, by whatever means necessary, to keep its damned self within the limits set by The Constitution.