Hi Ben,
Your estimate using IPUMS ACS data is including people living in group quarters, which are not considered households by Census. When restricting your data to respondents with GQ values of 1,2, and 5, IPUMS ACS data should give you an estimate of 120,756,015 for the total number of households in 2019. Though the numbers still don’t perfectly match, this discrepancy is due to official statistics being calculated from restricted-access data that is not available through IPUMS.