A 10kw heat strip delivers 34,120 BTU/hr which is already something like 2x the entire heat load of most 1056' homes in MO, so it would more than cover you even if the heat pump was fratzed.
That would be 32 BTU/hr per square foot of conditioned space. A typical code-min new home that size would come in between 10-15 BTU/ft at an outside temp of 0F. (
99% outside design temps in MO range between +2F and +15F, depending on location. It get's colder than that for 1% of the heating season hours, but doesn't dwell at those temps long enough to matter, from a heating-plant sizing point of view.) Even if it leaked a lot of air and had the legal-maximum window/floor area ratio it would be tough to have a heat load more than 10kw, or 34,120 BTU/hr.
If yours is an older home with 2-wythe brick walls, and no wall insulation, with single pane windows (without storm windows), you might have a heat load as big as 34 KBTU/hr, but not more than the combined output of the heat pump + 10kw heat strips.
If the ducts for the heat pump are in an unconditioned attic, above the insulation rather than in a basement that will add some to the heating system sizing. Air sealing of both the ducts and the ceiling where they penetrate the attic insulation is critical in that type of installation.