Agreed. Cruz' incidental Canadian citizenship was irrelevant to his qualifications for the Senate.
The NBC issue for the presidency has never been adjudicated, but would likely become an issue in the event of a Cruz nomination.
However, given the prior experience and judicial opinions regarding a.) the Chester A. Arthur presidency, b.) the George Romney candidacy and c.) the Ted Cruz candidacy-to-date, the odds would seem to favor Cruz being eligible.
Not to mention the Barack Obama presidency which, with the Chester A. Arthur presidency, totally negates the belief that NBC requires both parents be born in America.
Chester Alan Arthur was born October 5, 1829, in Fairfield, Vermont.[a][7] Arthur's mother, Malvina Stone, was born in Vermont, the daughter of George Washington Stone and Judith Stevens. Malvina's family was primarily of English descent, and her grandfather, Uriah Stone, fought in the Continental Army during the American Revolution.[7] His father, William Arthur, was born in Dreen, Cullybackey, County Antrim, in what is now Northern Ireland; he graduated from college in Belfast and emigrated to Canada in 1819 or 1820. Arthur's mother met his father while William Arthur was teaching at a school in Dunham, Quebec, just over the border from her native Vermont. The two married in Dunham on April 12, 1821, soon after meeting.[7] After their first child, Regina, was born, the Arthurs moved to Vermont.