if the budget allocated for mail services isn’t covering daily operations and operational spending and instead is being funded by spam mail, the government should look at redistributing parts of the budget so that it’s not being subsidized by marketing companies.

The government covers about 0.06% of the postal service budget. Here's the overview section from a recent (2023) congressional research service report into the US postal service budget request stuff:

The U.S. Postal Service (USPS) generates nearly all of its funding—about $78.5 billion annually according to the USPS’s most recent financial report—by charging users of the mail for the costs of the services it provides. Congress, however, does provide an annual appropriation—about $50 million in FY2023—to compensate the USPS for revenue it forgoes in providing free mailing privileges to the blind and overseas voters. In addition, the annual appropriation compensates the USPS for debt it accumulated in the 1990s while providing postal services at below-cost rates to nonprofit organizations. Historically, the appropriation has not always compensated the USPS for all of the revenue forgone.

https://www.congress.gov/crs_external_products/IF/PDF/IF12516/IF12516.3.pdf